Pull cord device and window covering including the same

[0021]Referring to FIGS. 1 to 6, a window covering 2 is shown to comprise a header rail 21, a base rail 22, a plurality of slats 23, and a pull cord device 3.

[0022]The base rail 22 is movable relative to the header rail 21 in an upright direction. The slats 23 are disposed between the header rail 21 and the base rail 22. The preferred embodiment of the pull cord device 3 according to this invention includes a container 30, a spring driving unit 40, pull cords 50, a braking unit 60, and a one-way damper unit 90. The container 30 is disposed on the header rail 21 in this embodiment, but may be disposed on the base rail 22 in other embodiments of this invention. In this embodiment, the container 30 includes a hollow base part 31 and a cover part 32 to cover an open side of the base part 31. The spring driving unit 40 is disposed in the container 30, and includes first and second cord spools 41, 42 and a spring motor that biases the first and second cord spools 41, 42 to rotate in a cord-w