US 4,055,023 AGranted

Door operator with instant reverse feature

AssigneeVemco Products, Inc.

InventorsGeoffrey H. Gatland, Kenneth L. Robitaille

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Abstract

An improved garage door operator of the motor-driven chain-and-sprocket type comprising a molded plastic gear case assembly supporting an output shaft for rotation relative thereto. A molded plastic worm wheel is loosely disposed on the shaft for limited rotation relative thereto and is driven by a reversible electric motor through a worm. Camming surfaces on the worm wheel and a second element which is fixedly disposed on the shaft form a low-torque coupling such that under normal conditions the motor drives the shaft to move the garage door. If the door encounters an obstacle and is unable to move, continued rotation of the motor drives the cam surface of the second element up the cam surface of the wheel so as to axially shift the second element relative to the gear case to trip a reversing switch. Up and down limits are established by means of a small threaded shaft which is driven off of the worm wheel and which produces linear displacement of a limit switch actuator traveler. The traveler carries adjustable dogs which operate respective limit switches in a limit switch carrier which is mounted on the gear case.

In a door operator:

a motor for moving the door between up and down limits;
an operator body;
an output shaft supported by the body for rotation relative thereto:
means operated by said shaft for mechanical connection to the door to move the door as the shaft rotates;
a first cam element non-rotatably disposed on the shaft and spaced from the operator body;
a second cam element loosely rotatably disposed on the shaft for at least limited rotation relative thereto between the first cam element and the operator body and bearing against the operator body;
drive means connecting the motor to the second cam element, said first and second cam elements being urged into complemental contact with one another to form a torque coupling between the motor and the shaft capable of transmitting torques less than a predetermined value and responsive to torques in excess of said value to cause said cam elements to slip relative to one another and to cause axial shaft of the first cam element away from the second element and the body;
and means carried by the body responsive to the axial shift of said first element to alter the operation of said motor, the operator further including limit means carried by the body for establishing said up and down limits of door travel, the limit means comprising a threaded shaft rotatably carried by the operator body, drive means connected between the second cam element and the threaded shaft to drive same, limit switch actuator means comprising traveler means threadedly engaging the shaft and responsive to the rotation thereof to move axially therealong a distance related to shaft rotation, first and second switch means electrically connected to the motor for controlling actuation thereof in respectively opposite directions of rotation, said first and second switch means being arranged to be actuated by said traveler at respective positions thereof representing said limits of travel, said second cam element comprising an integrally molded worm wheel of first diameter and having peripheral teeth, a hollow cylindrical portion of second diameter less than the first extending axially from said worm wheel and terminating in a second peripherally toothed gear, said second peripherally toothed gear being mechanically connected to drive the threaded shaft such that the output shaft may shift axially inside of the second cam element without disturbing the mechanical drive between the second cam and threaded shaft.

5 more elements

Abstract

Claims14