Importance

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Abstract

A counterbalanced door assembly particularly suited for heavy-duty load bearing applications such as sidewalk access doors, and for precasting into concrete slabs, comprises a door, a frame surrounding the door, a hinge connecting the door to the frame for rotation about a first axis, a torque rod arm mounted to rotate about a second axis displaced from the first axis, and one or more torque rods. One end of the torque rod arm is connected to the torque rod to twist the torque rod as the torque rod arm rotates about the second axis thereby generating a counterbalance force. A force control mechanism, which may be a cam with a properly shaped cam surface or a link hinged at either end, receives the counterbalance force from the torque rod arm and applies it in a controlled direction over a controlled effective moment arm relative to the first axis to generate the desired counterbalance torque.

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First Claim