GB2440318A

GB2440318A - Cyclone separator outlet arrangement and noise reduction means

Info

Publication number: GB2440318A
Application number: GB0614897A
Authority: GB
Inventors: David Benjamin Smith; Kevin Smith
Original assignee: Hoover Ltd
Current assignee: Hoover Ltd
Priority date: 2006-07-27
Filing date: 2006-07-27
Publication date: 2008-01-30
Also published as: GB0614897D0; WO2008012579A1

Abstract

A cyclone separator, and an associated vacuum cleaner, having a cyclone chamber 15 for separating matter contained in the airflow, An inlet duct 14 for the flow of fluid extends tangentially into the upper end of the cyclone through the sidewall 10 thereof. The upper end of the cyclone chamber 15 is closed by an upper end wall 11 and a tubular outlet duct or so-called vortex finder 12 extends into the cyclone chamber 15 from the upper end wall 11. A cross member 13 extends across the upstream end of the vortex finder 12 between circumferentially-spaced wall portions 10 thereof. The cross member 13 mechanically stiffens the vortex finder 12 and helps to reduce noise-generating vibrations. The cross member also serves to disrupt the airflow at the inlet to the vortex finder, 12 thereby preventing any airflows which may induce resonance. The axial length of the member is no more than 10mm and the width less than 5mm.

Description

Cyclone Separator This invention relates to a cyclonic separator and to

a vacuum cleaner incorporating the same.

It is well known to use cyclonic separators as a means for separating dirt and dust from an airflow in a vacuum cleaner. Indeed, the increased popularity of such so-called cyclonic vacuum cleaners has lead to much research and development activity aimed at improving the separation efficiency of cyclones and adapting the cyclone principle to render it suitable for use in domestic applications. However, experience has shown that the high velocities and turbulence of the airflow in cyclones contributes significantly to the overall noise level generated by the vacuum cleaner in use.

In conventional cyclones of the reverse-flow type, the cleaned air leaves the cyclone chamber through an outlet tube or so-called vortex finder, which projects axially into the cyclone chamber from one end thereof. A substantial part of the noise generated by the cyclone is attributable to the air entering the vortex finder. In addition to the noise produced by turbulence in the airflow, loud whistling noises can be caused by resonance.

EP1653837 attempts to overcome the above-mentioned problem of noise by providing axially extending grooves along the internal surface of the vortex finder..

The provision of the grooves is also purported to improve pressure recovery along the how path of the cleaner.

GB241 3974 also attempts to overcome the above-mentioned problem of noise by providing an axially extending baffle, which projects radially inwardly from an internal surface of the vortex finder. The baffle may be supplemented by the provision of the grooves disclosed in EP1 653837.

EP1 066115 further attempts to overcome the above-mentioned problem of noise by providing a body or proboscis, which extends along the centre axis of the vortex finder. Although this arrangement is effective at reducing noise, the solution increases the manufacturing cost of the cleaner and renders the cyclone susceptible to blockage by coarse particulate matter. GB2399780 attempts to overcome the problem of blockage by providing a plurality of cyclones without the centre body, as a means of achieving noise reduction whilst avoiding the propensity to blockage.

GB241 8630 discloses another attempt to overcome the above-mentioned problem by providing a plurality of axially extending baffles, which project radially from the internal surface of the vortex finder from respective circumferentially spaced points.

In a further embodiment, the upstream-end of the baffles are inclined relative to the direction of flow. The provision of the baffles is complex and again renders the vortex finder susceptible to blockage by cause particulate matter.

We have now devised a cyclonic separator which alleviates the above-mentioned problems.

In accordance with the present invention, there is provided a cyclone separator comprising a cyclone chamber for separating matter contained in a fluid flow, and a fluid inlet duct and a fluid outlet duct communicating with the chamber, the outlet duct extending axially of the rotational axis of the cyclone, wherein a cross member extends across an upstream end of the outlet duct between circumferentially-spaced wall portions thereof.

The outlet duct forms a vortex finder for the cyclonic airflow in the cyclone chamber.

The provision of the cross member at the upstream end of the outlet duct mechanically stiffens the duct and helps to reduce noise-generating vibrations. The cross member also serves to disrupt the airflow at the inlet to the vortex finder, thereby preventing any airf lows which may induce resonance.

In trials, it was found that such an arrangement reduced the generated noise from 89 to 86 dBa. The arrangement also totally eliminated any whistling noises.

Preferably the cyclone chamber comprises a tubular portion which projects axially into the cyclone chamber, the cross member being provided at the upstream end of said tubular portion.

Preferably the cross member comprises an upstream end edge, which lies in substantially the same plane as the upstream end edge of the tubular portion of the outlet duct.

Preferably the cross member extends through the central longitudinal axis of the outlet duct.

Preferably the cross member extends between diametrically opposed portions of the internal surface of the outlet duct. A plurality of intersecting cross members may be provided.

Preferably the cross member comprises generally parallel sidewalls, which extend axially of the outlet duct.

Preferably the cross member comprises generally parallel opposite end walls, which extend normal to the longitudinal axis of the outlet duct.

Preferably the cross member is confined to a region at the upstream end of the outlet duct having an axial length of no more than 10mm. Preferably the region has an axial length of 5mm.

Preferably the cross member has a width of less than 5mm and preferably 2mm.

Preferably the cross member is formed Integrally with said outlet duct.

Also in accordance with the present invention, there is provided a vacuum cleaner having a cyclone separator which comprises a cyclone chamber for separating matter contained in a fluid flow, and a fluid inlet duct and a fluid outlet duct communicating with the chamber, the outlet duct extending axially of the rotational axis of the cyclone, wherein a cross member extends across an upstream end of the outlet duct between circumferentially-spaced wall portions thereof.

An embodiment of the present invention will now be described by way of an example only and with reference to the accompanying drawings, in which: Figure 1 is a sectional view along a longitudinal axis of a cyclone separator in accordance with the present invention; Figure 2 is a sectional view along the line Il-Il of Figure 1; and Figure 3 is a perspective view of the upstream end of a vortex finder of the cyclonic separator of Figure 1.

Referring to the drawings, there is shown a cyclonic separator of the kind typically used in domestic vacuum cleaners. The separator comprises a circular-section tubular sidewall 10, which may be frusto-conical as shown although this is not essential. An inlet duct 14 for the flow of fluid extends tangentially into the upper end of the cyclone through the sidewall 10 thereof.

The upper end of the cyclone is closed by an upper end wall 11. A tubular outlet duct or so-called vortex finder 12 extends into the cyclone chamber 15 from the upper end wall 11. The central longitudinal axis of the vortex finder 12 is aligned with the central longitudinal axis of the cyclone chamber 15. A rectangular-section cross member 13 extends diametrically across the lower end of the vortex finder 12. The cross member 13 comprises an upstream end edge, which lies in substantially the same plane as the lower end edge of the tubular portion of the vortex tinder 12.

The cross member 13 comprises generally parallel sidewalls, which extend axially of the vortex finder 12 and generally parallel opposite end walls, which extend normal to the longitudinal axis of the vortex finder 12. The cross member has an axial length of approximately 5mm and a width of approximately 2mm.

In use the upper end of the vortex finder 12 is connected to a fan which draws air through the inlet 14 and out of the chamber 15. The tangential orientation of the inlet 14 with respect to the sidewall 10 of the chamber creates a cyclonic airflow, whereby air spirals downwardly around the chamber 15 towards its lower end. As the air flows downwards, the volume of air in the spiral flow is constantly being diminished by virtue of it having been drawn radially inwardly and upwardly towards the vortex finder 12.

As the air swirls, dirt and dust in the airflow are forced radially outwardly against the interior of the wall 10 by the radially outwards component of the force acting on the particles. The dirt and dust thus separated remains in an edge zone of the chamber and is carried downwardly by the flow until it reaches the point where the cyclonic flow ceases, whereupon the dirt and dust is deposited at the lower region of the chamber 15.

The cross member 13 mechanically stiffens the vortex finder 12 and helps to reduce noise-generating vibrations. The cross member 13 also serves to disrupt the airflow at the inlet to the vortex finder 12, thereby preventing any airf lows which may induce resonance.

A vacuum cleaner in accordance with the present invention is substantially quieter in operation than a vacuum cleaner which does not have a cross-member extending across the vortex finder 12. The arrangement is mechanically simple and does not significantly affect the passage of any dirt and dust to any downstream separation stage.

Claims

CLAIMS

1. A cyclone separator comprising a cyclone chamber for separating matter contained in a fluid flow, and a fluid inlet duct and a fluid outlet duct communicating with the chamber, the outlet duct extending axially of the rotational axis of the cyclone, wherein a cross member extends across an upstream end of the outlet duct between circumterentially-spaced wall portions thereof.

2. A cyclone separator as claimed in claim 1, in which the outlet duct is disposed at one end of the chamber, the inlet duct also being disposed at said end of the chamber.

3. A cyclone separator as claimed in claims 1 or 2, in which the cyclone chamber comprises a tubular portion which projects axially into the cyclone chamber, the cross member being provided at the upstream end of said tubular portion.

4. A cyclone separator as claimed in claim 3, in which the cross member comprises an upstream end edge, which lies in substantially the same plane as the upstream end edge of the tubular portion of the outlet duct.

5. A cyclone separator as claimed in any preceding claim, in which the cross member extends through the central longitudinal axis of the outlet duct.

6. A cyclone separator as claimed in claim 5, in which the cross member extends between diametrically opposed portions of the internal surface of the outlet duct.

7. A cyclone separator as claimed in any preceding claim, in which a plurality of intersecting cross members are provided.

8. A cyclone separator as claimed in any preceding claim, in which the cross member comprises generally parallel sidewalls, which extend axially of the outlet duct.

9. A cyclone separator as claimed in any preceding claim, in which the cross member comprises generally parallel opposite end walls, which extend normal to the longitudinal axis of the outlet duct.

10. A cyclone separator as claimed in any preceding claim, in which the cross member is confined to a region at the upstream end of the outlet duct having an axial length of no more than 10mm.

11. A cyclone separator as claimed in claim 10, in which the region has an axial length of approximately 5mm.

12. A cyclone separator as claimed in any preceding claim, in which the cross member has a width of less than 5mm.

13. A cyclone separator as claimed any preceding claim, in which the cross member is formed integrally with said outlet duct.

14. A cyclone separator substantially as herein described with reference to the accompanying drawings.

15. A vacuum cleaner having a cyclone separator as claimed in any preceding claim.