Abstract:
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.
Abstract:
Methods and apparatus for sensing barrier position in a barrier movement system are disclosed. Electrical apparatus is connected to the barrier and generates a barrier position signal representative of barrier positions which may be used by a controller to detect barrier position. The electrical apparatus can be manually adjusted to reflect a first barrier position such as a closed position. Other barrier positions can be sensed by comparing the barrier position signal to other manually adjustable position signals.