Patent ID: 8418742

Claim:
An automatic brake mechanism for a cord drive, comprising: a drive cord spool mounted for rotation in a first direction and in a second direction about a first shaft defining a first axis of rotation; a drive cord including first and second ends, wherein said first end is secured to said drive cord spool; a release arm mounted for rotation in a first direction and in a second direction about said first axis of rotation; a spring defining a relaxed position and having a first end attached to said first shaft and a second end attached to said release arm, and defining an outer circumference of said spring wherein said outer circumference is reduced when said first end of said spring is brought toward said second end of said spring, and wherein said spring engages said drive cord spool to stop rotation of said drive cord spool when said release arm is rotated in one of said first and second directions; wherein the rotation of said release arm in one of said first and second directions about said first axis of rotation results in said first end of said spring being brought toward said second end of said spring; and wherein said drive cord spool defines an inner surface and said spring resides inside said inner surface such that, when said first end of said spring is brought toward said second end of said spring such that said outer circumference of said spring is reduced, said spring releases said inner surface of said drive cord spool allowing rotation of said drive cord spool about said first axis of rotation, and when said spring is back at said relaxed position said outer circumference of said spring engages said inner surface of said drive cord spool, preventing further rotation of said drive cord spool about said first axis of rotation; a spring actuator mounted for rotation in a first direction and in a second direction about said first axis of rotation; and a transform gear mounted for rotation in a first direction and in a second direction about a second shaft defining a second axis of rotation wherein said transform gear engages said release arm and said spring actuator such that rotation in one of said first and second directions of said release arm about said first axis of rotation results in rotation of said actuator arm in an opposite direction from that of said release arm, and wherein said first end of said spring is attached to said spring actuator wherein rotation of said spring actuator in one of said first and second directions about said first axis moves said first end of said spring toward said second end of said spring.