Importance

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Abstract

An automatic-locking mechanical drive construction for raising and lowering a window covering, including a fixed cylindrical shaft, a rotary drive member mounted to rotate about an axis with respect to the shaft, and a rotary driven member turnable with respect to the shaft and about the axis of the drive member. The drive and driven members have pairs of facing, abuttable walls effecting a two-directional, lost-motion rotary driving connection between the members, and a helical coil spring is disposed on the shaft, so as to frictionally seize it, and selectively lock thereon. The spring has a radially-projecting shoulder intermediate its ends. Spaced-apart shoulders on the driven member are individually engageable with the projecting shoulder on the spring whereby the spring normally prevents turning of the driven member in either of opposite directions. Lugs on the driving member respectively engage end portions of the spring to unlock its grip on the shaft, thereby enabling the abuttable walls of the driven and drive members to turnably drive the driven member in either of two directions as the drive member is turned in either of opposite directions.

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First Claim