Abstract: A safety mechanism for a power operated door activates limit switches for stopping an electric motor or reverses it's polarity. The safety mechanism is more compact than existing types of mechanisms and is suitable for friction drive roller garage door openers. Furthermore, indicator lights are provided that indicates exactly when a limit switch is tripped enabling field adjustment of the safety mechanism to suit specific pressures to either stop or reverse the door. The mechanism includes a worm slidably mounted on a motor drive shaft, with a cage structure around the worm to slide with the worm, two compression springs supporting the cage structure in a neutral position, an actuator member on the cage structure to activate limit switches when the cage structure slides in either direction, and adjustment screws to vary the position of the limit switches, each limit switch having an indicator light indicating when the switch is activated.

Abstract: A power operating device for use with vertically sliding garage doors provides a friction drive roller that can slide laterally to take into account variations in space between the side of the upper panel of the door and the guide tracks when the door is open or closed.