The Chamberlain Group, Inc.

Robert E Dutka

Robert John Olmsted

William Chen

Andrew Gavel

Phillip McCartney

Phillip A Mccartney

A cable tension sensing apparatus is mounted on a wall having a door opening. The jack shaft garage door operator includes a drive unit having an electric motor for driving a jack shaft mounted above a door opening. A pull-up cable drum is connected to the jack shaft and has a multi-strand steel pull-up cable that may be payed out to lower a door or wound up to raise the door. The cable tension sensing apparatus includes a cable guide to retain the cable a substantially fixed distance from the wall and a spring driven cable follower which urges against the cable extending between the drum periphery and the cable guide. An alerting switch is connected to the cable follower and sends a signal indicating loss of cable tension when the cable follower moves beyond a predetermined distance. Additionally, the movement of the cable follower moves a door blocking arrangement to a position to block movement of the door when being raised without use of the motor.

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Glen Ellyn, IL, United States of America

Robert E Dutka