Domestic cyclonic vacuum cleaner

Abstract

A cyclonic vacuum cleaner including a suction inlet fluidly connected in series to a vac-motor for drawing a dirty airflow in through the suction inlet. The suction inlet is fluidly connected downstream to both a first cyclonic separator and to a flow device via a flow junction, the flow junction configured for dividing the dirty airflow into two separate airflows, a first airflow passing through the first cyclonic separator and a second airflow passing through the flow device, thus stepping down the dirty airflow through the first separator compared to the dirty airflow through the suction inlet. The flow device is either a second cyclonic separator, an air filter or an air turbine. A screening member is upstream of the flow device for screening out dirt particles from the second airflow so that the dirt particles are retained in the first airflow, thus concentrating dust loading in the first airflow.

Claims

1. A domestic cyclonic vacuum cleaner comprising a suction inlet fluidly connected in series to a vac-motor for drawing a dirty airflow in through the suction inlet, the suction inlet being fluidly connected downstream to both a first cyclonic separator and to a flow device, said fluid connection to the first cyclonic separator and to the flow device being via a flow junction for dividing the dirty airflow into two separate airflows: a first airflow passing through the first cyclonic separator and a second airflow passing through the flow device; the flow device being either a second cyclonic separator or an air turbine, and wherein a screening member is provided upstream of the flow device and comprises a plurality of apertures that are configured for screening out dirt particles based on size from the second airflow so that the screened-out dirt particles are retained instead in the first airflow.

2. The domestic cyclonic vacuum cleaner of claim 1, wherein the first cyclonic separator has a tangential air inlet.

3. The domestic cyclonic vacuum cleaner of claim 1, wherein the first cyclonic separator and the flow device are both upstream of the vac-motor.

4. The domestic cyclonic vacuum cleaner of claim 1, wherein the flow device is a second cyclonic separator, the second cyclonic separator being arranged to have a smaller cut size than the first cyclonic separator for separating out from the second airflow fine dirt particles which, by virtue of particle size, have passed through the screening member.

5. The domestic cyclonic vacuum cleaner of claim 4, wherein a third cyclonic separator is connected in series to either the first cyclonic separator or the second cyclonic separator, the third cyclonic separator also being connected in parallel to the second cyclonic separator when connected in series to the first cyclonic separator or in parallel to the first cyclonic separator when connected in series to the second cyclonic separator.

6. The domestic cyclonic vacuum cleaner of claim 5, wherein the third cyclonic separator is downstream of the first cyclonic separator when connected in series to the first cyclonic separator or downstream of the second cyclonic separator when connected in series to the second cyclonic separator.

7. The domestic cyclonic vacuum cleaner of claim 6, in which the third cyclonic separator has a smaller cut size than the first cyclonic separator when connected in series to the first cyclonic separator or a smaller cut size than the second cyclonic separator when connected in series to the second cyclonic separator.

8. The domestic cyclonic vacuum cleaner of claim 1, wherein the suction inlet is connected to the first separator by a first duct and the flow junction comprises an opening in a wall of the duct.

9. The domestic cyclonic vacuum cleaner of claim 8, wherein the screening member is provided across the opening.

10. The domestic cyclonic vacuum cleaner of claim 9, wherein the opening is provided in a section of the first duct which progressively reduces in cross-sectional area.

11. The domestic cyclonic vacuum cleaner of claim 1, in which the cut size X.sub.1 of the first cyclonic separator is within 30% of the cut size X.sub.s of the screening member (0.7 X.sub.s<X.sub.1<1.3 X.sub.s).

12. The domestic cyclonic vacuum cleaner of claim 1, wherein screening member is configured so that coarser dirt particles are concentrated in the first airflow and finer dirt particles are concentrated in the second airflow.

13. A domestic vacuum cleaner comprising a suction inlet fluidly connected in series to a vac-motor for drawing a dirty airflow in through the suction inlet, the suction inlet being fluidly connected downstream to both a first dust separator and to a flow device, said fluid connection to the first dust separator and to the flow device being via a flow junction for dividing the dirty airflow into two separate airflows: a first airflow passing through the first dust separator and a second airflow passing through the flow device; the flow device being either a second dust separator or an air turbine, and wherein a screening member is provided upstream of the flow device and comprises a plurality of apertures that are configured for screening out dirt particles based on size from the second airflow so that the screened-out dirt particles are retained instead in the first airflow.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic diagram illustrating the principal layout of a cyclonic vacuum cleaner in accordance with the invention;

(3) FIG. 2 is a schematic diagram illustrating in more detail a flow junction forming part of the layout in FIG. 1;

(4) FIG. 3 is a graph illustrating the respective grade-efficiency curves for a first and second cyclonic separator forming part of the layout in FIG. 1;

(5) FIG. 4 is a schematic diagram illustrating series connection of a first and third cyclonic separator; and

(6) FIG. 5 is a schematic diagram illustrating series connection of a second and third cyclonic separator.

DETAILED DESCRIPTION OF THE INVENTION

(7) The cyclonic vacuum cleaner 1 illustrated schematically in FIG. 1 comprises a cleaner head 3 having a suction inlet 3a, a first cyclonic separator 5, a second cyclonic separator 7 and a vac-motor 9. These components are fluidly connected together, via ducting, in a series-parallel arrangement (analogous to a combination circuit in electrical circuitry) whereby the cleaner head 3 and vac-motor 9 are connected in series and the first separator 5 and second separator 7 are connected in parallel between the cleaner head 3 and the vac-motor 9. In operation therefore, the vac-motor 9 draws a dirty airflow Qd in through the suction inlet 3a on the cleaner head 3, which then divides into a first airflow Q1 passing through the first separator 5 and a second airflow Q2 passing through the second separator 7 before re-combining as a clean airflow Qc passing through the vac-motor 9.

(8) The dirty airflow Qd divides into the first airflow Q1 and second airflow Q2 at a flow junction 11 provided upstream of the first separator 5 and the second separator 7.

(9) An enlarged view of the flow junction 11 is shown in FIG. 2. It comprises a branch duct 13 which branches off from an opening 15 in the wall of a main duct 17 carrying the dirty airflow Qd from the cleaner head 3. The main duct 17 connects to the inlet (not shown) of the first separator 5 and carries the first airflow Q1. The branch duct 13 connects to the inlet (not shown) of the second separator 7 and carries the second airflow Q2.

(10) The relative flow restrictions presented by the first and second separator are arranged such that the majority of the flow70% of the dirty airflow Qdis diverted through the second separator 7. Only a relatively small fraction of the flowthe remaining 30% of the dirty airflow Qdis sent through the first separator 5. Consequently, there is a significant step-down in the flow through the first separator 5, which helps optimize the flow rate through the first separator 5 whilst nevertheless maintaining a high flow rate through the suction inlet 3a on the cleaner head 3.

(11) The first separator 5 itself is of conventional design comprising a single, relatively large diameter, tangential-inlet cyclone 5a having a cut size D50 (see FIG. 3) and communicating with a first dust collector (not shown).

(12) The second separator 7 is likewise of conventional design comprising a plurality of relatively small diameter, parallel cyclones 7a each having a cut size d50 (see FIG. 3) and each communicating with a second dust collector (not shown).

(13) The cut size d50 is smaller than the cut size D50, so that the smaller cyclones 7a in the second separator 7 are better able than the larger cyclone 5a in the first separator 5 to separate out smaller particles from the dirty airflow.

(14) A screening member in the form of a mesh screen 19 is provided across the opening 15 in the wall 17. The mesh screen 19 is of conventional woven construction. A different screening member may be used, for example an etched foil mesh or a louvered grille.

(15) In operation, the mesh screen 19 functions to screen out coarse dirt particles from the second airflow Q2 so that they are retained instead in the first airflow Q2. This concentrates the coarse dirt in the first airflow Q2, advantageously increasing the solids loading at the tangential inlet to the first separator 5 to help maximize separation efficiency. The cut size Xs of the mesh screen 19 is matched to the cut size D50 of the first separator 5 so that the first separator 5 is effectively tuned to target the coarse dirt which is screened out by the mesh screen 19 and which therefore remains in the first airflow Q1.

(16) At the same time, the mesh screen 19 operates to reduce overloading of the second separator 7 by relatively large dirt particles, instead, the second separator 7 is loaded only with fine dirt particles which, by virtue of their size, have passed through the mesh screen 19.

(17) The first and second separators 5, 7 thus together constitute a single stage of separation (denoted A in FIG. 1), but incorporating two parallel separation paths, a coarse dirt path through the first separator 5 and a fine dirt path through the second separator 7. In this manner, the arrangement effectively combines aspects of a conventional two-stage series separation system in a single, energy-efficient combi-stage, the conventional primary cyclonic stage is replaced by the first cyclonic separator 5, and the conventional secondary cyclonic stage is replaced, at least in part, by the second cyclonic separator 7 operating in parallelnot in serieswith the first cyclonic separator 5. This is made possible by the provision of the mesh screen 19.

(18) The mesh screen 19 is air-scrubbed continuously by the airflow in the main duct 17, to help keep the mesh screen 19 clean. In order to promote good scrubbing, the main duct 17 narrows in the region of the mesh screen 19 to maintain the scrubbing velocity across the upstream surface of the mesh screen 19.

(19) In alternative embodiments the second cyclonic separator 7 may be replaced by a different flow device altogether, such as an air turbine or air filter. In these arrangements, the excess airflow through the cleaner head (i.e. in excess of the desired optimal flow at the inlet to the first separator 5) is still used advantageously to perform useful work in parallel with the first separator 5.

(20) The flow junction 11, first separator 5 and flow device (e.g. second separator 7) may alternatively be placed downstream of the vac-motor 9, so that the vac-motor pushes the dirty airflow through the first separator 5 and the flow device.

(21) In an alternative embodiment (not illustrated) the outlet of the first cyclonic separator 5 may be connected to the inlet of the flow device. So, for example, the outlet of the first cyclonic separator 5 may be connected to the inlet of the second cyclonic separator 7. In this arrangement, the dirt particles not separated by the first cyclonic separator 5 may be separated by the second cyclonic separator 7. Care must be taken here not to overload the second cyclonic separator 7 with coarse dirt particles, this may be achieved by appropriately tuning the cut sizes D50 and d50.

(22) A third cyclonic separator may be provided downstream of either the first cyclonic separator or the second cyclonic separator. For example, a third cyclonic separator 21 may be located in series with the first separator 5, downstream of the first separator 5, to remove some of the dirt particles which are not separated by the first separator 5 (see FIG. 4). A third cyclonic separator 21 may alternatively (or additionally) be positioned in series with the second cyclonic separator, downstream of the second separator (see FIG. 5). The third separator forms part of the same combi-stage A which comprises the first and second separators 5,7, and the third cyclonic separator 21 advantageously makes use of a parallel connection with either the first or second cyclonic separator 5, 7 (as the case may be) in order to help minimize the total pressure drop across the combi-stage A.

(23) Although not illustrated, an additional separation stage may be connected in series with the combi-stage A, downstream of the combi-stage A, to remove particlespossibly very small particulatesnot removed by the combi-stage A. This additional separation stage may be cyclonic, or may comprise one or more air filters.