VORTEX FINDER FOR A CYCLONIC SEPARATOR

Abstract

The invention describes a vortex finder for a cyclonic separator. The vortex finder includes a plurality of stationary vanes around which incoming air is guided into the vortex finder, in which a side of the vanes facing the incoming air is provided with a protrusion at a stagnation point. The protrusion is shaped so as to guide the incoming air into the vortex finder, and have a concave side following a shape of a neighboring vane, and a rounded top. Further, the protrusion has a height in a range between 70% and 130%, and in a range between 85% and 115% of a gap width between the vanes. The gap width between adjacent vanes increases from an outside to an inside of the vortex finder. A vacuum cleaner that includes a cyclonic separator has such a vortex finder.

Claims

1. A vortex finder for a cyclonic separator, the vortex finder comprising: a plurality of stationary vanes around which incoming airguided into the vortex finder, wherein a side of the plurality of stationary vanes facing the incoming airis provided with a protrusionat a stagnation point.

2. The vortex finder of claim 1, wherein the protrusionis shaped so as to guide the incoming air into the vortex finder.

3. The vortex finder of claim 1 or 2, wherein the protrusion has a concave side following a shape of a neighboring vane.

4. The vortex finder of claim 1, wherein the protrusion has a rounded top.

5. The vortex finder of claim 1, wherein the protrusion has a height in a range between 70% and 130% of a gap width between the plurality of stationary vanes.

6. The vortex finder of claim 5, wherein the protrusion has the height in a range between 85% and 115% of the gap width between the plurality of stationary vanes.

7. The vortex finder of claim 1, wherein a gap width between adjacent vanes of the plurality of stationary vanes increases from an outside to an inside of the vortex finder.

8. The vortex finder of claim 1, wherein a vacuum cleaner comprising a cyclonic separator includes the vortex finder.

9. The vortex finder of claim 3, wherein sides of the protrusion facing into the vortex finder are concave, and sides of the protrusion facing outside of the vortex finder are convex.

10. The vortex finder of claim 9, wherein the concave sides of the protrusions are shaped such that there is a continuous curve from basic shape of a vane of the plurality of stationary vanes towards top of the protrusion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows an airflow as happens with vanes covered by our non-prepublished copending application EP 19158400.2; and

[0011] FIGS. 2A-4B illustrate embodiments of a vortex finder in accordance with the present invention.

DESCRIPTION OF EMBODIMENTS

[0012] FIG. 1 shows an airflow as happens with vanes covered by our non-prepublished copending application EP 19158400.2 (attorney’s docket 2019P00168EP). While most of the air flow enters into the vortex finder F as a result of suction by the motor-fan aggregate of the vacuum cleaner (not shown), in reality, some of the air flow bumps into the vane V, and another part goes around the vane V. Where the air bumps into the vane V, dirt will be accumulated. The place where the air bumps into the vane V, is called the stagnation point S, which is usually defined (see e.g. Wikipedia) as a point in a flow field where the local velocity of the fluid is zero. Stagnation points exist at the surface of objects in the flow field, where the fluid is brought to rest by the object.

[0013] In accordance with preferred embodiments of the invention, a side of the vanes V facing the incoming air A is provided with a protrusion P at the stagnation point S, to thereby prevent dirt from accumulating on the vanes V at the stagnation points S. By doing so, the pollution can be significantly reduced, without influencing the separation performance or pressure loss.

[0014] It is noted that while the protrusions P are described here in the context of vanes V having only one sharp edge E where air separates from the vane V inside of the vortex finder F, covered by our non-prepublished copending application EP 19158400.2, the problem of dirt accumulation at stagnation points where air bumps into the vanes of the vortex finder, and the solution of providing the sides of the vanes with protrusions, is not limited to such vanes, and may equally happen with different vanes (e.g. those described in US2012167336 or WO2015150435), which will likewise benefit from protrusions to prevent dirt accumulation from happening.

[0015] It is important that the protrusions P are positioned as close as possible to the stagnation points S. FIG. 12b of WO 2015150435 shows outer trailing end edges 45 resulting from cutting a part out of vanes 41. However, that solution will not help to prevent dirt from accumulating inside the hollow parts at the trailing end faces 42 in which the stagnation points are located. So, in this prior art solution, at the stagnation points, there are no protrusions that prevent dirt from accumulation at the stagnation points, but hollow shapes that collect dirt.

[0016] FIGS. 2A and 2B show a first embodiment of vanes V provided with protrusions P to prevent dirt from accumulating. Here, both sides of the protrusions P are concave.

[0017] FIGS. 3A and 3B show a second embodiment of vanes V provided with protrusions P to prevent dirt from accumulating. Here, the sides of the protrusions P facing into the vortex finder F are concave, and the sides of the protrusions P facing the outside of the vortex finder F are convex.

[0018] The concave shapes of FIGS. 2A - 3B serve to ensure that the protrusions P are shaped so as to guide the incoming air A relatively smoothly into the vortex finder F.

[0019] The protrusions P preferably have a rounded top, which is more forgiving as regards manufacturing tolerances than a sharp top. However, a sharp top is possible.

[0020] In a practical embodiment, the vanes are separated by gaps having a gap width of about 1.75 mm; with a different gap width, the size of the other dimensions discussed below needs to be scaled accordingly.

[0021] In the embodiment of FIGS. 2A and 2B, the design goal that the protrusions P are positioned as close as possible to the stagnation points S means that the protrusions P preferably deviate by less than 1 mm from the stagnation points S. The diameter of any rounded tops of the protrusions P is preferably in a range between 0.25 mm and 0.35 mm, such as about 0.3 mm. Compared to the basic shape of the vanes as shown in FIGS. 1-4, the height of the protrusions P is preferably in a range between 0.75 mm and 1.25 mm, such as about 1 mm. The footprint of the protrusions P is preferably in a range between 2.5 mm and 3.5 mm, such as about 3 mm.

[0022] In the embodiment of FIGS. 3A and 3B, the concave sides of the protrusions P are preferably shaped in such a way that a gap width between adjacent vanes V is substantially constant, i.e. these concave sides follow the shape of the neighboring vanes.

[0023] Compared to the basic shape of the vanes as shown in FIGS. 1-4, the height of the protrusions P is preferably in a range between 1.25 mm (70% of the gap width of 1.75 mm) and 2.25 mm (130% of 1.75 mm), and more preferably in a range between 1.5 mm (85% of 1.75 mm) and 2.0 mm (115% of 1.75 mm), such as about 1.75 mm, which most nicely results in the protrusions P being located at the stagnation points S. The concave sides of the protrusions P are preferably shaped in such a way that there is a continuous curve from the basic shape of the vane towards the tops of the protrusions P. The diameter of any rounded tops of the protrusions P is preferably in a range between 0.15 mm and 0.25 mm, such as about 0.2 mm.

[0024] In the embodiments of FIGS. 4A and 4B, the protrusions P are shaped such that the gap width between adjacent vanes V increases from the outside towards the inside of the vortex finder F. The gap width increase is preferably gradually and/or continuously. As a result, the gap obtains a diffuser-like shape. Diffusers are known from e.g. I.E. Idel’chik -Handbook of hydraulic resistance (1960). The gap width increase (here between curved shapes of neighboring vanes V) is preferably comparable to a gap width increase between flat plates positioned at an angle of between 5° and 30°, and more preferably about 12°. In one example, the gap has an initial width W.sub.i of 0.9 mm, and, beyond the protrusion P, an end width W.sub.e of 1.75 mm. The protrusion P has a rounded top, a height of 2.3 mm, and a footprint FP of 7 mm.

[0025] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The claimed feature that the vanes V have a protrusion P at a stagnation point S does not mean that the protrusion P must be exactly at the stagnation point S, but merely that the protrusions P are positioned close to the stagnation points S. Measures recited in mutually different dependent claims may advantageously be used in combination.