Multistage cyclone and surface cleaning apparatus having same
A hand vacuum cleaner may have a first stage cyclone having a first stage cyclone chamber and a second stage cyclone downstream from the first stage cyclone and at least substantially nested in the first stage cyclone. A screen is positioned laterally outwardly from the second stage cyclone and defines a passage positioned between an inner side of the screen and the outer wall of the second stage cyclone. The screen extends axially at least about 70% of a length of the second stage cyclone chamber.
1. A hand vacuum cleaner having a front end and a rear end, the hand vacuum cleaner comprising:
(a) a first stage cyclone having a first stage cyclone chamber, a first stage cyclone air inlet, a first stage cyclone air outlet and a first stage longitudinal cyclone axis about which the air rotates in the first stage cyclone chamber, the first stage cyclone chamber having a length in a direction of the first stage longitudinal cyclone axis;
(b) a second stage cyclone downstream from the first stage cyclone and at least substantially nested in the first stage cyclone, the second stage cyclone having a second stage cyclone chamber, a second stage cyclone air inlet, a second stage cyclone air outlet and a second stage longitudinal cyclone axis about which the air rotates in the second stage cyclone chamber, the second stage cyclone chamber having a length in a direction of the second stage longitudinal cyclone axis; and,
(c) a screen positioned laterally outwardly from the second stage cyclone and defining a passage positioned between an inner side of the screen and the outer wall of the second stage cyclone, the screen extending axially at least about 70% of a length of the second stage cyclone chamber.
2. The hand vacuum cleaner of claim 1 wherein the screen extends axially at least about 80% of a length of the second stage cyclone chamber.
3. The hand vacuum cleaner of claim 1 wherein the screen extends axially at least about 90% of a length of the second stage cyclone chamber.
4. The hand vacuum cleaner of claim 1 wherein the second stage cyclone has a second stage dirt collection chamber located at one axial end of the second stage cyclone chamber and the screen extends axially from a position proximate the second stage dirt collection chamber to an opposed axial end of the second stage cyclone chamber.
5. The hand vacuum cleaner of claim 1 wherein the passage has a cross sectional area in a direction transverse to air flow therethrough and the cross sectional area of the passage is about equal to a cross sectional area of the first stage cyclone air inlet in a direction transverse to a flow direction therethrough.
6. The hand vacuum cleaner of claim 1 wherein the passage has a cross sectional area in a direction transverse to air flow therethrough and the cross sectional area of the passage is about equal to a cross sectional area of the second stage cyclone air outlet in a direction transverse to a flow direction therethrough.
7. The hand vacuum cleaner of claim 1 wherein the second stage cyclone has a plurality of second stage cyclone air inlets and the passage has a cross sectional area in a direction transverse to air flow therethrough and a combined cross-sectional area of the second stage cyclone air inlets in a direction transverse to a flow direction therethrough is about equal to the cross sectional area of the passage in a direction transverse to air flow therethrough.
8. The hand vacuum cleaner of claim 1 wherein the second stage cyclone air inlet is located at an end of the passage and is provided in a sidewall of the second stage cyclone chamber.
9. The hand vacuum cleaner of claim 8 wherein the second stage cyclone air inlet comprises a vane extending into the passage and, in a direction of air flow along the vane, having a downstream end located at the sidewall of the second stage cyclone chamber.
10. The hand vacuum cleaner of claim 1 wherein the screen is made of metal.
11. A vacuum cleaner comprising:
(a) a first stage cyclone having a first stage cyclone chamber, a first stage cyclone air inlet, a first stage cyclone air outlet and a first stage longitudinal cyclone axis about which the air rotates in a rotational direction in the first stage cyclone chamber;
(b) a second stage cyclone downstream from the first stage cyclone and at least substantially nested in the first stage cyclone, the second stage cyclone having a second stage cyclone chamber, a second stage cyclone air inlet, a second stage cyclone air outlet and a second stage longitudinal cyclone axis about which the air rotates in the second stage cyclone chamber; and,
(c) a screen positioned laterally outwardly from the second stage cyclone and defining a passage positioned between an inner side of the screen and the outer wall of the second stage cyclone
wherein the second stage cyclone air inlet is located at an end of the passage and directs air into the second stage cyclone chamber in the rotational direction.
12. The vacuum cleaner of claim 11 wherein the second stage cyclone air inlet is provided in a sidewall of the second stage cyclone chamber.
13. The vacuum cleaner of claim 11 wherein the second stage cyclone air inlet comprises a vane located in the passage and, in a direction of air flow along the vane, having an upstream end located proximate the screen and a downstream end located proximate the second stage cyclone chamber.
14. The vacuum cleaner of claim 13 wherein the vane is integrally formed as part of a sidewall of the second stage cyclone chamber.
15. The hand vacuum cleaner of claim 13 wherein the second stage cyclone has plurality of second stage cyclone air inlets each of which comprises a vane.
16. The vacuum cleaner of claim 11 wherein the screen is made of metal.
17. The vacuum cleaner of claim 11 wherein the screen has a plurality of openings at least some of which extend in about the direction of rotation.
18. The vacuum cleaner of claim 11 further comprising a second stage outlet screen having a plurality of openings at least some of which extend in about the direction of rotation.