Washing machine

1. A washing machine comprising:

an outer tub holding wash water;

an inner tub rotatably provided in the outer tub; and

a pulsator rotatably provided in the inner tub, the pulsator comprising:

a base comprising a hub formed at a center thereof; and

a plurality of ribs protruding from the base, each rib comprising:

an upper surface extending outwardly along a radial direction to meet an outer circumference of the base; and

a side surface declining from the upper surface to the base, the side surface comprising:

a first side surface having a boundary with the base, the boundary radially diverging outward in a circumference direction, the boundary meeting an inner circumference of the base; and

a second side surface extending from the first side surface to meet the outer circumference of the base and the upper surface,

wherein the first side surface is formed integrally with the second side surface to form a continuously curved surface, and

wherein the first and second side surfaces progressively broaden in an outward radial direction.

2. The washing machine of claim 1 , wherein the first side surface declines to the base more steeply than the second side surface.

3. The washing machine of claim 1 , wherein the upper surface is curved.

4. The washing machine of claim 3 , wherein as the upper surface extends outwardly in the radial direction, a first curved surface that is recessed toward the base and a second curved surface extending from the first curved surface to meet the outer circumference of the base and convexly protruding are formed continuously from the upper surface, and

wherein the first and second curved surfaces progressively broaden in an outward radial direction.

5. The washing machine of claim 4 , wherein a lowest point where a distance between the upper surface and the base becomes minimal is formed on a first curve that the first curved surface and the side surface form, a highest point where the distance between the upper surface and the base becomes maximal is formed on a second curve that the second curved surface and the side surface form, and the first curved surface is extended from the hub such that the highest point is located between the lowest point and the outer circumference of the base, and the second curved surface is extended from the first curved surface to meet the outer circumference of the base.

6. The washing machine of claim 5 , wherein a distance from the lowest point to the highest point is greater than a distance from the highest point to the outer circumference of the base.

7. The washing machine of claim 5 , wherein the highest point is located closer to the outer circumference of the base than the hub.

8. The washing machine of claim 5 , wherein the first side surface and the second side surface have different inclination directions about a boundary between the first side surface and the second side surface.

9. The washing machine of claim 4 , wherein the base comprises a convergent portion that is recessed between adjacent ribs from among the plurality of ribs.

10. The washing machine of claim 9 , wherein the convergent portion defines a plurality of holes that communicate the inner tub and the outer tub.

11. The washing machine of claim 4 , wherein the upper surface progressively broadens in an outward radial direction to meet the outer circumference of the base.

12. The washing machine of claim 1 , wherein the side surface is formed at both sides of the upper surface.

13. A washing machine comprising:

an outer tub holding wash water;

an inner tub rotatably provided in the outer tub; and

a pulsator rotatably provided in the inner tub, the pulsator comprising:

a base comprising a hub formed at the center thereof; and

a plurality of ribs protruding from the base, each rib comprising:

an upper surface extending outwardly along a radial direction to meet an outer circumference of the base; and

a side surface declining from the upper surface to the base, the side surface comprising:

a first side surface extending radially and diverging outwardly in a circumference direction such that a contact area with laundry is gradually broadened; and

a second side surface forming a curved surface in a body along with the first side surface and extending from the first side surface to meet the upper surface and the outer circumference of the base, in order to reduce flow resistance caused by the wash water in the inner tub,

wherein a boundary between the first side surface and the base meets an inner circumference of the base,

wherein the first side surface is formed integrally with the second side surface to form a continuously curved surface, and

wherein the first and second side surfaces progressively broaden in an outward radial direction.

14. The washing machine of claim 13 , wherein the first side surface declines to the base more steeply than the second side surface.

15. The washing machine of claim 13 , wherein the first side surface and the second side surface have different inclination directions about a boundary between the first side surface and the second side surface.

16. The washing machine of claim 13 , wherein the side surface is gradually broadened toward the outer side along the radial direction to meet the outer circumference of the base.

17. The washing machine of claim 13 , wherein the base comprises a convergent portion that is recessed between adjacent ribs from among the plurality of ribs.