EP2078488B1 - Device to remove dust from air full of dust, especially for use in a vacuum cleaner - Google Patents

Description

The invention relates to a device for separating dust from dust-laden air, in particular for use in a vacuum cleaner, in the form of a cyclone separator, in which the air is supplied to an at least approximately rotationally symmetrical container via a tangentially arranged inlet and after flowing through a dust collection chamber an axially disposed outlet is discharged.

In vacuum cleaners, in particular vacuum cleaner, dust retention systems are used, which are usually arranged between the air inlet of a dust collection chamber and the suction side of a fan and hold back the absorbed dust before entering the fan. The best known variant is a bag shaped filter which is internally pressurized, d. h., the dust settles inside the bag. The bag is usually still downstream of a fine dust filter, which receives dust particles in the order of less than 2 microns, which pass through the bag. The removal of this dust content from the room air wins with the increasing number of people with allergies in importance, as these particles are respirable because of their small size and therefore lead to a health burden. When reaching the maximum capacity, which is about 400 grams, the bag must be replaced, this can be hygienic especially with closable bags, as the dust remains in the bag and is disposed of with this. Such replacement is required several times a year, depending on usage, and incurs costs. Also, the fine dust filter must be replaced after a certain period of use, but here are the intervals because of the small amount of fine dust larger, from the manufacturers, a replacement after about a year is recommended. Because of the small particle sizes, a small proportion by mass of fine dust is produced, which is why commercially available fine dust filters have a capacity of about 10 grams.

In some micro-cleaners, multi-purpose vacuum cleaners or commercial appliances, there are external filters surrounding the blower. The advantage is the greater absorption capacity, the disadvantage is that the filters of this vacuum cleaner are designed only for coarse dust, the particulate matter, which allergenic pollen and microorganisms includes, passes through the filter and is blown back into the room by the fan and even stirred up.

• kompakter Aufbau;
• hygienische Entnahmemöglichkeit des gesammelten Staubs;
• geringe Saugleistungsverluste;
• geringe Geräuschentwicklung.

There is a desire for a reusable filter system for coarse dust which has the following properties:

• compact construction;
• hygienic removal of the collected dust;
• low suction power losses;
• low noise.

1. 1. auswaschbare und wiederverwendbare Textilfilterbeutel ( DE 199 11 331 C1 ); hier bestehen in erster Linie Bedenken hinsichtlich der Hygiene, da die stark verunreinigten Beutel zunächst manuell geleert und anschließend in der Waschmaschine gewaschen werden müssen;
2. 2. Staubkassetten aus porösem Sintermaterial ( EP 1 179 312 A2 );
3. 3. Fliehkraft-Abscheider, auch Zyklon-Abscheider genannt ( EP 0 647 114 B1 ).

Essentially the following systems are known here:

1. 1. Washable and reusable textile filter bags ( DE 199 11 331 C1 ); Here, there are primarily hygiene concerns, since the heavily contaminated bags must first be manually emptied and then washed in the washing machine;
2. 2. Dust cassettes made of porous sintered material ( EP 1 179 312 A2 );
3. 3. centrifugal separator, also called cyclone separator ( EP 0 647 114 B1 ).

The latter two systems offer the possibility to easily remove the dust collector, empty and clean when dirty. In commercially available systems, in particular in the cyclone separators, attempts have been made to replicate the dust deposits known from the dust bags. For this reason, the separation limit of the separators at blower outputs of 1500 to 2200 watts, which are common in ordinary household vacuum cleaners, is very low and there are large quantities of respirable particulate matter in the Staubsammelbehältem. The emptying of these containers then causes the lighter components of the dumped dust to fly up and spread in the air. As a result, in particular allergy sufferers are charged.

To avoid this, is in the WO 2007/022959 A2 proposed to use a Staubentscheide system based on a inertia separator, with which the dust can be separated into three fractions, the separation limits are with dust particle sizes of 200 microns (1st stage) and 30 microns (2nd stage). In an advantageous embodiment, a dust binder is added to the second fraction, in which the majority of the dust particles have a size between 30 .mu.m and 200 .mu.m. It may then be advantageous if directed air swirling takes place in the sump that receives this second fraction to mix dust particles and dust binder. Such Luftverwirbelung does not take place in the dust collector of the above inertia separator.

From the DE 10 2006 046 328 B4 a cyclone separator is known which consists of a combination of a tangential separator and an axial separator. The axial separator is preceded by a funnel-shaped collar.

The EP 1 985 217 A2 and the EP 1 602 308 A1 show cyclone separator, where the outlet is preceded by a funnel-shaped area. However, this does not contribute to changing the flow rate, as parts of the outlet are perforated behind the funnel.

The invention thus presents the problem to disclose a device for separating dust from dust-laden air, which is based on the one hand on the principle of the cyclone separator and therefore causes turbulence of the dust particles in the dust collector and in which on the other hand, the separation limit far beyond the particle size of respirable particulate matter (less than 2 μm).

According to the invention, this problem is solved by a device having the features of patent claim 1. Advantageous embodiments and further developments of the invention will become apparent from the following subclaims.

The advantages attainable with the invention result from the fact that the container is designed such that the flow velocity of the air flow in the inflow region of the outlet is less than in the region of the inlet in that the mean distance of the inlet from the axis of symmetry is less than the radius of the outlet , This ensures that only large particles remain in the dust collection chamber.

Figur 1

einen Zyklon-Abscheider herkömmlicher Bauart,

Figur 2

eine Prinzipskizze eines verbesserten Zyklon-Abscheiders,

Figur 3

den Zyklon-Abscheider nach Figur 1 mit verbessertem Tauchrohr,

Figur 4

den Zyklon-Abscheider nach Figur 2 mit einer Prallplatte.

An embodiment of the invention is shown purely schematically in the drawings and will be described in more detail below. It shows

FIG. 1

a cyclone separator of conventional design,

FIG. 2

a schematic diagram of an improved cyclone separator,

FIG. 3

the cyclone separator after FIG. 1 with improved dip tube,

FIG. 4

the cyclone separator after FIG. 2 with a baffle plate.

FIG. 1 shows a tangential flowed cyclone separator of conventional design. This is constructed from an at least approximately rotationally symmetrical, here cylindrical container 1 and has a tangentially arranged inlet 2, via which the air is supplied, and an axially arranged outlet in the form of a protruding into the container 1 dip tube 2. The lower part of the container, which is traversed by the dust-laden air on the way from the inlet 2 to the outlet 3, acts as a dust collecting chamber. 4

The air passes at an inlet velocity v _E through the inlet 2 into the container 1 on a circular path with the radius r _E , which corresponds to the average distance of the inlet 2 from the symmetry axis 5 of the container 1. In this case, an air vortex is generated with the angular momentum L, which is proportional to the product of inlet radius and velocity: $$\mathrm{L}={\mathrm{v}}_{\mathrm{e}}{\mathrm{xr}}_{\mathrm{e}}$$

The air leaves the container 1 through the outlet 3, wherein the air vortex contracts to the radius r _{T of} the dip tube 3. Here is the angular momentum conservation theorem
L = constant
applies, results for the tangential velocity v _T on the dip tube 3: $${\mathrm{v}}_{\mathrm{T}}={\mathrm{v}}_{\mathrm{e}}{\mathrm{xr}}_{\mathrm{e}}/{\mathrm{r}}_{\mathrm{T}}$$

In conventional cyclone separators, r _{E is} always significantly larger than r _T ; usually two to four times. However, this means that the tangential velocity v _T on the dip tube 3 also Also, two to four times higher than the inlet velocity v _E at the inlet 2. For the deposition of the entrained dust particles, the centrifugal acceleration a _T on the dip tube is crucial, applies to the applies $${\mathrm{a}}_{\mathrm{T}}\approx {{\mathrm{<figure-callout\; id="2"\; label="v\; T"\; filenames="imgf0001.png"\; state="\{\{state\}\}">v\; </figure-callout>}}_{\mathrm{T}}}^{\mathrm{2}}$$

For given v _E , the centrifugal acceleration is therefore increased by a factor of 4 - 16. As a result, even the smallest particles are deposited. The separation limit of these cyclone separators is in the order of 1 micron for the existing in household vacuum cleaner blower power in the range of 1500 to 2200 watts.

1. 1. Durch die niedrige Trenngrenze von ca. 1 µm können sie zwar einen Staubbeutel nahezu ersetzen, belasten beim Entleeren die Atemluft aber mit sehr viel lungengängigem Feinstaub.
2. 2. Durch die hohen Geschwindigkeiten werden auch die Druckverluste durch den Zyklon sehr hoch.
3. 3. Außerdem führen die hohen Geschwindigkeiten noch zu einer erheblichen Geräuschentwicklung.

Conventional cyclone separator in vacuum cleaners therefore have the following disadvantages:

1. 1. Due to the low separation limit of approx. 1 μm, they can almost replace a dust bag, but pollute the breathing air when emptying, but with a lot of respirable fine dust.
2. 2. The high speeds also make the pressure losses through the cyclone very high.
3. 3. In addition, the high speeds still lead to a significant noise.

The in FIG. 2 shown separator avoids these disadvantages by not accelerating the air flowing into the dust collecting chamber 14 in the lower part of the container 11 air, but slows down. This is achieved in that, according to the invention, the radius r _{T2 of} the dip tube 13 is greater than the mean distance r _{E2 of} the inlet 12 from the axis of symmetry 15. The air enters the container at the inlet velocity v _E with a very small radius r _E2 . Downward, the container 11 and the dip tube 13 widen in a funnel shape. Thus, the radius of the vortex generated in the inlet region is increased towards the inflow region of the dip tube 13, and therefore the flow velocity of the air flow is decelerated due to the angular momentum conservation law and the wall friction. The tangential velocity v _T2 is then reduced by at least a factor of 10 in comparison with conventional cyclone separators with tangential flow. This not only minimizes pressure loss and noise, but also shifts the cut-off to 20-30 μm. In the dust collector 14 therefore no particulate matter remains and it can be emptied without dust.

FIG. 3 shows in longitudinal section a separator, in which by an advantageous embodiment of the dip tube 13, the separation of fine dust is further improved. For this purpose, the inflow region of the dip tube 13 is surrounded by a grid 16 which has a closed bottom 17. The grid-shaped structure fulfills two Functions: It even out the flow that enters the dip tube 13 and thus improves the selectivity of the cyclone separator. In addition, it acts as a protection for a downstream fine filter (not shown). In case of malfunction (eg cyclone clogged or improperly closed bottom flap 18) otherwise larger amounts of coarse dirt could get into the fine filter and clog it. Both functions could be realized by the grid 16 shown, but also by a screen structure or a perforated plate. The grid arrangement has the advantage that it is easier to clean. Not only in the event of malfunctions, but also in normal operation, fibers can occasionally get caught in the flow straightener.

In addition to the vortex described above, there is still a predominantly vertical secondary flow (indicated by the arrows 19), the dirt particles that have accumulated by centrifugal force and gravity at the bottom of the container, can stir up again. The dip tube 13 is therefore fluidly closed down through the grid floor 17, so that the deposited particles are not yet stirred up and transported on.

• ein konischer Ring 20, der die Sekundärströmung nach innen lenkt,
• und eine runde Prallplatte 21, deren Durchmesser in etwa dem kleinsten Durchmesser des konischen Ringes entspricht und die die noch vorhandene Vertikalkomponente der Sekundärströmung blockiert.

A further improvement is to provide a calmed collection area in which the secondary flow is so greatly attenuated that it can no longer agitate the deposited particles. Figure 4 shows the installation measures with which such a calmed collection area can be achieved. They are

• a conical ring 20 which directs the secondary flow inward,
• and a round baffle plate 21, whose diameter corresponds approximately to the smallest diameter of the conical ring and which blocks the remaining vertical component of the secondary flow.

Larger particles (> 30 .mu.m), which are deposited in the region of the dip tube grille 16, pass through the secondary flow and the force of gravity into the gap 22 between conical ring 20 and baffle plate 21. Here they are forced outwards by the centrifugal force and by gravity and thus arrive in the lower part of the dust collecting container 14 between bottom flap 18 and baffle plate 21st

The original cyclone vortex is only slightly hindered by the internals 20 and 21, since they are rotationally symmetric. Therefore, it is present even in the collection area in a weakened form and can be used to mix the deposited dust with a binder.

Ring 20 and baffle plate 21 are shown here in interaction, but they also reduce individually already the vertical component of the secondary flow 19th

Claims (8)

1. A device for separating dust from dust-laden air, in particular for use in a vacuum cleaner, said device being in the form of a cyclone separator having an at least nearly rotationally symmetric container (11) to which the air is fed through a tangentially disposed inlet (12), the air then being passed through a dust collection chamber (14) and subsequently discharged through an axially disposed outlet,
   Characterized in that,
   the container (11) is configured such that the flow velocity of the air flow in the inflow region of the outlet (3) is lower than in the region of the inlet (12), wherein the mean distance (r_E2) of the inlet (12) from the axis of symmetry (15) is smaller than the radius (r_T2) of the outlet
2. The device as recited in claim 1,
   wherein the container (11) widens from the inlet (12) toward the dust collection chamber (14), the widened portion preferably having the shape of a funnel.
3. The device as recited in one of the preceding claims,
   wherein the outlet (3) takes the form of a dip tube (13) extending into the dust collection chamber (14).
4. The device as recited in claim 3,
   wherein the dip tube (13) tapers in the manner of a funnel, starting at its inflow region.
5. The device as recited in claim 3 or 4,
   wherein the inflow region of the dip tube (13) is surrounded by a screen or grid (16).
6. The device as recited in claim 5,
   wherein the screen or grid (16) has a closed bottom (17).
7. The device as recited in claim 5 or 6,
   wherein the grid (16) is surrounded by a conical ring (20), in particular in the area of the bottom (17).
8. The device as recited in claim 7,
   wherein a baffle plate (21) is disposed below the ring (20).

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