Vortex finder for a cyclonic separator
A vortex finder ( 18,27,40 ) for a cyclonic separator ( 1 ) through which air flowing in a helical path ‘D’ about an axis A-A of a cyclone chamber ( 4 ) passes to an outlet ( 6 ) is disclosed. The vortex finder comprises a plurality of stationary overlapping vanes ( 13,19 ) extending in an axial direction and spaced radially around said axis ‘A’, the vanes ( 13,19 ) being positioned relative to each other so a helical flow of air about the axis of the cyclone chamber ( 4 ) passes over an outer surface ( 16 ) of the vanes ( 13,19 ) with a portion of the air flow being redirected around a leading edge ( 14 ) of each vane ( 13,19 ) and through a gap between adjacent vanes ( 13,19 ) to the outlet ( 6 ). At any point along the axis, a portion of an outer surface ( 16,20,30,46 ) of each vane ( 13,19,28,41 ) lies on a circle having its center coaxial with said axis, the outer surface ( 16,20,30,46 ) of each vane ( 13,19,28,41 ) having a portion leading towards the leading edge ( 14,33,47 ) that extends inwardly away from the circle so that the leading edge ( 14,33,47 ) of each vane ( 13,19,28,41 ) about which air is redirected through the gap between vanes ( 13,19,28,41 ) is located within a region bound by said circle to create a region of overpressure on the outer surface ( 16 ) of the adjacent vane ( 13,19 ) in the vicinity of the gap.
1. A vortex finder for a cyclonic separator for allowing air flowing about an axis of a cyclone chamber to pass to an outlet, the vortex finder comprising:
a plurality of stationary vanes, each stationary vane having a leading edge, a trailing edge and an outer surface extending between the leading edge and the trailing edge,
wherein the plurality of stationary vanes are spaced radially around said axis when installed in a cyclone chamber, the vanes being positioned relative to each other for allowing a flow of air about the axis of the cyclone chamber to pass over an outer surface of the vanes with a portion of the air flow being redirected around the leading edge of each vane through a gap between the trailing edges of adjacent vanes to the outlet, and
wherein, at any point along the axis, a portion of the outer surface of each vane lies on a circle having its center coaxial with said axis, the outer surface of each vane having a portion leading towards the leading edge that extends inwardly away from the circle so that the leading edge of each vane about which air is redirected through the gap between the training edges of adjacent vanes is located within a region bound by said circle.
2. A vortex finder according to claim 1 , wherein the portion of said outer surface extending inwardly away from the circle is arcuate in shape.
3. A vortex finder according to claim 1 , wherein the outer surface of each vane has a portion that extends outwardly from the trailing edge towards the circle and in a direction of airflow across the vanes.
4. A vortex finder according to claim 3 , wherein said portion that extends outwardly from the trailing edge is arcuate in shape.
5. A vortex finder according to claim 1 , wherein each vane has a face that defines a recessed region positioned to receive air directed against said vane from the leading edge of a preceding vane to create said region of overpressure in said recessed region.
6. A vortex finder according to claim 1 , wherein an angle between a first plane (T 1 ) that extends at a tangent to the outer surface at the leading edge of a vane and a second plane (T 2 ) that extends at a tangent to the outer surface of an adjacent vane at a point where the first plane (T 1 ) intersects said adjacent vane is greater than 15 degrees.
7. A vortex finder according to claim 1 , wherein said portion of the outer surface of each vane that lies on a circle at any point along the axis has an radius R, and said portion of the arcuately shaped outer surface of each vane that extends inwardly towards the axis has a radius r, wherein r<R.
8. A vortex finder according to claim 7 , wherein the radius r of said portion of the arcuately shaped outer surface of each vane that extends inwardly towards the axis is greater than 0.2 mm.
9. A vortex finder according to claim 1 , wherein for each vane, the outer surface of a vane narrows or tapers towards the leading edge of the vane.
10. A vortex finder according to claim 1 , wherein for each vane, the outer surface of a vane tapers towards the trailing edge of the vane.
11. A vortex finder according to claim 1 , wherein the vanes extend in a helical path about the axis.
12. A vortex finder according to claim 11 , wherein the vanes taper inwardly towards the axis.
13. A cyclonic separator comprising a vortex finder according to claim 1 .
14. A vacuum cleaner comprising the cyclonic separator according to claim 13 .
15. A cyclonic separator according to claim 13 , wherein the portion of said outer surface extending inwardly away from the from the circle is arcuate in shape.
16. A cyclonic separator according to claim 13 , wherein the outer surface of each vane has a portion that extends outwardly from the trailing edge towards the circle and in a direction of airflow across the vanes.
17. A cyclonic separator according to claim 13 , wherein each vane has a face that defines a recessed region positioned to receive air directed against said vane from the leading edge of a preceding vane to create said region of overpressure in said recessed region.
18. A vacuum cleaner according to claim 14 , wherein at least said inwardly extending portion of said outer surface is arcuate in shape.
19. A vacuum cleaner according to claim 14 , wherein the outer surface of each vane has a portion that extends outwardly from the trailing edge towards the circle and in a direction of airflow across the vanes.
20. A vacuum cleaner according to claim 14 , wherein each vane has a face that defines a recessed region positioned to receive air directed against said vane from the leading edge of a preceding vane to create said region of overpressure in said recessed region.