of the Venetian blind at one lateral side of the slats for pulling by hand. The slat lift cord is inserted through the slats and connected between the bottom rail of the blind and one end of the external lift cord. The user can pull the external lift cord to move the slat lift cord, and to further control the elevation of the blind. Pulling the external lift cord can simultaneously move the lift lock between the locking position and the unlocking position. Therefore, the user can adjust the blind to the desired elevation by means of operating the external lift cord. Because the external lift cord is suspended from the headrail of the blind at one side of the slats, it is conveniently accessible. However, because theexternal lift cord is not kept out of reach of children, children may pull the external lift cord for fun. In case the external lift cord is hung on a child""s head, a fetal accident may occur. Furthermore, the external lift cord tends to be tangled with the tilt cord of the tilt control mechanism or the slats of the blind.
Taiwan Patent No. 149396 (application no. 8722193) discloses a Venetian blind lifting control mechanism, which uses a winding spring to automatically take up the external lift cord after each operation. When stopped at a particular elevation, the return force of the spring, the weight of the blind, and the friction force between the lift cord and the related elements are maintained in balance, keeping the blind positioned in