Cyclone such as for use in a surface cleaning apparatus

1. A cyclone for a surface cleaning apparatus comprising:

(a) a cyclone chamber having a first end having a first end wall, a second end having a second end wall, a sidewall and a cyclone axis of rotation, an air inlet and an air outlet are provided at the first end and a dirt outlet is provided at the second end, the air outlet comprises a screen that is positioned in the cyclone chamber; and,

(b) a dirt collection chamber external to the cyclone chamber, wherein the dirt outlet connects the dirt collection chamber in communication with the cyclone chamber,

wherein the sidewall and the first end wall meet at a first juncture and the air outlet and the first end wall meet at a second juncture, and

wherein the air inlet has a downstream end that is provided adjacent the first juncture, and

wherein the first end wall comprises a first juncture surface that extends radially inwardly from the sidewall, a second juncture surface that extends radially outwardly from the air outlet, and a central surface that joins the first and second juncture surfaces, and the first end wall has a portion that is on a side of the cyclone chamber opposed to the downstream end of the air inlet, the portion extends radially between the first and second junctures, is curved or inclined along the entire length of the portion from the first juncture to the second juncture and defines a non-planar lowermost surface in a plane in which the cyclone axis lies.

2. The cyclone of claim 1 wherein the central surface segment of the portion is curved along an entire length of the central surface segment of the portion from the first junction surface to the second junction surface in the plane in which the cyclone axis lies.

3. The cyclone of claim 1 wherein the first end wall is curved along the entire length of the first end wall from the first juncture to the second juncture in the plane in which the cyclone axis lies.

4. The cyclone of claim 1 wherein a portion of the downstream end of the air inlet adjacent the first juncture has an inlet radius and the first juncture surface has a first juncture radius that is the same as the inlet radius.

5. The cyclone of claim 4 wherein the second juncture surface has a second juncture radius that is the same as the inlet radius.

6. The cyclone of claim 1 wherein the screen has an inner end spaced axially inwardly from the air outlet and the inner end of the screen is positioned towards the dirt outlet.

7. The cyclone of claim 1 wherein the downstream end of the air inlet has a cross sectional area in a plane transverse to a direction of airflow through the downstream end of the air inlet, the downstream end of the air inlet has a diameter in the plane, and the air outlet is spaced inwardly from the sidewall at a location of the air inlet in a direction transverse to the cyclone axis by a sum of the diameter and an offset distance.

8. The cyclone of claim 1 wherein a plane that is transverse to the cyclone axis extends through the air inlet and a portion of the second juncture surface that is opposed to and faces the downstream end of the air inlet.

9. The cyclone of claim 8 wherein the portion of the second juncture surface that is opposed to and faces the downstream end of the air inlet is curved or inclined.

10. A surface cleaning apparatus comprising the cyclone of claim 1 wherein, when the surface cleaning apparatus is in use, the first end wall is a lower end wall of the cyclone chamber.

11. A cyclone for a surface cleaning apparatus comprising:

(a) a cyclone chamber having a first end having a first end wall, a second end having a second end wall, a cylindrical sidewall extending between the first and second end walls and a cyclone axis of rotation, an air inlet and an air outlet are provided at the first end and a dirt outlet is provided at the second end, the air outlet comprises a screen that is positioned in the cyclone chamber; and,

(b) a dirt collection chamber external to the cyclone chamber, wherein the dirt outlet connects the dirt collection chamber in communication with the cyclone chamber,

wherein the sidewall and the first end wall meet at a first juncture and the air outlet and the first end wall meet at a second juncture, and

wherein the air inlet has a downstream end that is provided adjacent the first juncture, and

wherein the first end wall comprises a first juncture surface that extends radially inwardly from the sidewall, a second juncture surface that extends radially outwardly from the air outlet, and a central surface which joins the first and second juncture surfaces, and the first end wall is curved or inclined along the entire length of the first end wall from the first juncture to the second juncture and defines a non-planar lowermost surface in a plane in which the cyclone axis, and

wherein a plane that is transverse to the cyclone axis extends through the air inlet and a portion of the second juncture surface that is opposed to and faces the downstream end of the air inlet.

12. The cyclone of claim 11 wherein each of the first and second juncture surfaces is curved in the plane in which the cyclone axis lies.

13. The cyclone of claim 11 wherein the first end wall has a portion that is on a side of the cyclone chamber opposed to the downstream end of the air inlet, the portion extends radially between the first and second junctures and the portion is curved or inclined.

14. The cyclone of claim 11 wherein the first end wall extends radially between the first and second junctures and the first end wall is curved along the entire length of the end wall from the first junction to the second junction in the plane which the cyclone axis lies.

15. The cyclone of claim 11 wherein a portion of the downstream end of the air inlet adjacent the first juncture has an inlet radius and the first juncture surface has a first juncture radius that is the same as the inlet radius.

16. The cyclone of claim 11 wherein the second juncture surface extends around all of the air outlet.

17. The cyclone of claim 11 , wherein the second junction surface:

includes a curved portion which is curved in the plane in which the cyclone axis lies and which has a second juncture radius that is larger than an inlet radius of a portion of the downstream end of the air inlet adjacent the first junction surface.