| 摘要 |
An operating system for a vertically movable collapsible covering includes lift cords anchored at an upper end to the top rail for the covering and at the bottom end on wrap spools which are either driven by coil springs or a reversible motor. The coil springs and motor via its transmission help counterbalance the shade so that it can be supported at intermediate positions between fully retracted and fully extended positions of the covering and lift cord guide pins are provided around which the lift cords can be wrapped to obtain a desired amount of friction to assist in rendering the covering counterbalanced regardless of the size and weight of the covering. The control system is confined within a dummy vane at the bottom of the fabric for the covering so as to be hidden from view.
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