| 摘要 |
A control system for a vertically moveable covering for an architectural opening includes a uni-directional drive assembly that is operated with a single pull element such that upon pulling of the pull element, the covering can be raised in increments. A clutch/brake assembly selectively prevents the covering from dropping by gravity between pulling strokes on the pulling element, but a release of the brake allows the shade to drop by gravity from its retracted position to any degree of extension. A governor is further provided to regulate the rate at which the covering drops by gravity. A cord lift system which is operated by the main drive assembly and the clutch/brake assembly includes a rotatable and axially slidable spool about which a lift cord can be wound. The lift cord has one end anchored to the spool and its opposite end extended through a supporting bracket for the spool and downwardly through the covering where the opposite end is anchored to a bottom rail such that a wrapping of the lift cord about the spool lifts the bottom rail thereby causing the covering to be raised adjacent to the lift spool. The lift cord is tangentially fed to the lift spool and forced into an angular wrap on the spool while an outer shell spaced a small distance from the spool prevents multiple wraps so that the lift cord does not become tangled. A return spring biases the spool in one direction to facilitate a controlled movement of the covering from a retracted to an extended position.
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