| 主权项 |
1. A covering for an architectural opening, comprising:
a rail; a covering for an architectural opening extending from said rail, said covering being extendable from and retractable toward said rail; a first shaft mounted in said rail for rotation in clockwise and counterclockwise directions about a first axis of rotation, said first shaft having a non-cylindrical profile and being operatively connected to said covering for extending and retracting said covering as the first shaft rotates; a first limiter operatively connected to said first shaft to stop the rotation of said first shaft upon extending the covering a desired distance, said first limiter including: a base fixed relative to the rail, said base defining a first set of threads and a first axially extending shoulder defining a first axially extending surface; a first hollow rod defining a second set of threads which are engaged with said first set of threads, wherein said first shaft extends through said first hollow rod and the first hollow rod and first shaft define mating profiles that cause the first hollow rod to rotate with the first shaft while allowing the first hollow rod to slide axially relative to the first shaft; said first hollow rod defining a second axially-projecting shoulder defining a second axially extending surface, wherein, as said first shaft rotates in a first direction, it causes the first hollow rod to rotate relative to the base, with the engaged threads causing the first hollow rod to slide axially relative to the first shaft until the first and second axially extending surfaces of the first and second axially-projecting shoulders abut each other, thereby stopping rotation of the first shaft in the first direction; a cord drive operatively connected to said first shaft, including a cord drive housing; a pulley mounted for rotation on said cord drive housing; and a cord wrapped onto said pulley, such that pulling on the cord causes rotation of said first shaft; wherein said pulley has an axis of rotation, the cord wraps around the pulley along a plane that is substantially perpendicular to the axis of rotation of the pulley, and further comprising a first bearing surface which supports said pulley for rotation, wherein at least a portion of said first bearing surface lies in said plane; and a second bearing surface which supports said pulley for rotation, wherein at least a portion of said second bearing surface lies in said plane.
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