Motor operated garage door mechanism

A motor operated garage door mechanism used to arrest the opening movement of a garage door should the door encounter an obstacle on its way up or to reverse its closing movement should the door encounter an obstacle on its way down, comprising, in combination:

• a housing;
• a shaft rotatively mounted in said housing;
• key means provided to prevent lateral movement of said shaft in said housing;
• a collar fixedly received on said shaft, said collar having a given rotational speed being driven by an electric reversing motor, said collar having protuding slants at opposite ends;
• two cylinders adjacent to said collar, said cylinders slidably received on said shaft and having protuding slants interlocking with the slants of said collar, said cylinders having a rotational speed proportioned to the given rotational speed of said collar, said cylinders having an external thread type spiral grooves;
• cable door closer actuating means operating in said grooves;
• a pair of adjustable limit switch means electrically connected to said motor and each oppositely disposed in a region adjacent to the extremities of said cylinders, said pair of limit switch means including a first limit switch for stopping said motor from rotating said collar and a second limit switch for causing said motor to reverse the rotation of said collar;
• a pair of compression springs means axially mounted on said shaft and disposed thereon on each side of said cylinders maintening said cylinders in working engagement with said collar, said cylinders being independently and longitudinally slidable on said shaft when the rotational speed of said cylinders varies from the given rotational speed of said collar whereby said pair of spring means allow one of the said cylinders when the rotational speed of said one cylinder differs from the given rotational speed of said collar to contact said first limit switch to stop the rotation of said collar when said one cylinder slides longitudinally away from said collar in one direction on said shaft and allow the other of the said cylinders when the rotational speed of said other cylinder differs from the given rotational speed of said collar to contact said second limit switch to reverse the rotation of said collar when said other cylinder slides longitudinally away from said collar in the other direction on said shaft.