CPC E06B 9/90 (2013.01) [E06B 9/76 (2013.01)] | 12 Claims |
1. A top-down bottom-up window covering, comprising:
a headrail;
a middle rail, which is movably provided below the headrail;
a bottom rail, which is movably provided below the middle rail;
a covering structure provided between the middle rail and the bottom rail;
a first rotating shaft, which is provided at the headrail and is adapted to receive or release a first cord, wherein an end of the first cord is fixed at the middle rail;
a second rotating shaft, which is provided at the headrail and is adapted to receive or release a second cord, wherein an end of the second cord is fixed at the bottom rail;
a lifting control structure provided at the headrail and adapted to control the first rotating shaft or the second rotating shaft to rotate;
a pre-stress unit, which is provided at the headrail and is concurrently movable along with the first rotating shaft; and
a one-way clutch, which is located between the first rotating shaft and the lifting control structure;
wherein, when the middle rail is pulled upward by the first cord, the one-way clutch is in an engaged state for keeping a link between the first rotating shaft and the lifting control structure;
when the middle rail is not pushed and not pulled upward by the first cord, and the bottom rail is lifted, the one-way clutch is in the engaged state for keeping the link between the first rotating shaft and the lifting control structure;
when the middle rail is pushed upward, the one-way clutch is in a disengaged state for breaking the link between the first rotating shaft and the lifting control structure, and a driving force provided by the pre-stress unit drives the first rotating shaft to receive the first cord.
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