Cyclonic separating apparatus
A cyclonic separating apparatus includes a chamber for separating dirt and dust from an airflow, an inlet to the chamber and a shroud. The shroud includes a wall having inner and outer surfaces and a multiplicity of through-holes forming an outlet from the chamber. Each through-hole has an axis. The inner surface of the wall has a serrated profile having a plurality of serrations arranged around at least a part of the circumference of the wall, each serration having a first face and a second face. At least one through-hole passes through the first face of at least one serration. By providing a plurality of serrations around the inner circumference of the wall, the airflow is forced to follow a longer path through each through-hole for when compared to conventional arrangements. This reduces the amount of dirt and dust which is able to pass through the shroud.
1. A cyclonic separating apparatus comprising a chamber for separating dirt and dust from an airflow, an inlet to the chamber and a shroud comprising a wall having a substantially circular cross-section, the wall comprising an inner surface, an outer surface upstream from the inner surface, and a multiplicity of through-holes forming an outlet from the chamber, each through-hole having an axis,
wherein the inner surface of the wall has a serrated profile comprising a plurality of serrations arranged around at least a part of a circumference of the wall, each serration having a first face and a second face, and at least one through-hole passes through the first face of at least one serration.
2. The cyclonic separating apparatus as claimed in claim 1 , wherein the axis of the at least one through-hole lies substantially parallel to the second face of the at least one serration.
3. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein the axis of the at least one through-hole lies at an angle to the first face of the at least one serration in the range of 60° to 120°.
4. The cyclonic separating apparatus as claimed in claim 3 , wherein the axis of the at least one through-hole lies substantially perpendicular to the first face of the at least one serration.
5. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein the first face of the at least one serration lies at an angle to the second face of the at least one serration in the range of 60° to 120°.
6. The cyclonic separating apparatus as claimed in claim 5 , wherein the first face lies substantially perpendicular to the second face.
7. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein the outer surface of the wall is curved and the axis of the at least one through-hole is arranged at an obtuse angle to the tangent of the curved outer surface of the wall at an upstream side of the through-hole.
8. The cyclonic separating apparatus as claimed in claim 7 , wherein the axis of the at least one through-hole is arranged at an angle in the range of 130° to 150° to the tangent of the curved outer surface of the wall at the upstream side of the through-hole.
9. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein the shroud has a longitudinal axis and at least some of the through-holes are arranged in a plurality of axially-extending columns, each column corresponding to a single serration on the inner surface of the wall.
10. The cyclonic separating apparatus as claimed in claim 9 , wherein the axes of each of the through-holes in a column lie substantially parallel to one another.
11. The cyclonic separating apparatus as claimed in claim 10 , wherein the axes of each of the through-holes in a column lie substantially perpendicular to the first face and substantially parallel to the second face of the respective serration.
12. The cyclonic separating apparatus as claimed in claim 9 , wherein the axes of the through-holes in at least two adjacent columns are parallel to one another.
13. The cyclonic separating apparatus as claimed in claim 12 , wherein the axes of the through-holes in at least four adjacent columns are parallel to one another.
14. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein at least some of the through-holes are spaced from one another at the inner surface of the wall by less than 1 mm.
15. The cyclonic separating apparatus as claimed in claim 14 , wherein at least some of the through-holes are spaced from one another at the inner surface of the wall by 0.6 mm or less.
16. The cyclonic separating apparatus as claimed in claim 15 , wherein at least some of the through-holes are spaced from one another at the inner surface of the wall by 0.4 mm or less.
17. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein at least some of the through-holes are spaced from one another at the inner surface of the wall by a distance which is 45% or less of the width or height of a through-hole.
18. The cyclonic separating apparatus as claimed in claim 17 , wherein at least some of the through-holes are spaced from one another at the inner surface of the wall by a distance which is 30% or less of the width or height of a through-hole.
19. The cyclonic separating apparatus as claimed in claim 18 , wherein at least some of the through-holes are spaced from one another at the inner surface of the wall by a distance which is 18% or less of the width or height of a through-hole.
20. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein the wall is cylindrical.
21. The cyclonic separating apparatus as claimed in claim 1 or 2 , wherein the wall is tapered.
22. A cleaning appliance comprising the cyclonic separating apparatus as claimed in claim 1 or 2 .
23. The cleaning appliance as claimed in claim 22 , wherein the cleaning appliance is a vacuum cleaner.