Electric circuit for a safety door edge

Claim 1

In a safety edge construction for an electrically powered door or the like, an electric circuit comprising at least three resiliently yieldably spaced flexible contact strips defining at least two strip pairs adapted to be deflected into respective successive contact by an obstruction in the path of door movement, conductor means connecting said strips in series with each other across a source of electric supply, and a pair of relays each having its coil connected in a respective strip pair and having contacts in circuit with door powering means, the contacts of one relay connected in the first deflected strip pair being closed when its coil is energized by normal operating circuit through these strips for maintaining the door powering circuit normally enabled, said one relay contacts operating upon contact of said first deflected strip pair to disable the powering circuit, the contacts of the other relay connected in the second deflected strip pair being independent of said one relay contacts and operative to reversely power the door, said other relay contacts being open when its coil is energized by normal operating current through the strips and closed upon contact of said second deflected strip pair to effect reverse powering of the door, whereby contact between said first deflected strip pair shunts said one relay to open its contacts and disable said door powering means, serverance of one of said contact strips precluding the normal operation of said one relay and requiring repair to effect normal operation and contact between said second deflected strip pair shunting said other relay coil to close its contacts and effect reverse powering to the door.