Dorma Door Controls, Inc.

Reading Door Closer Corporation

Sidney Lieberman

A control linkage for use with a door closer, wherein the linkage is provided with a spring which resiliently biases against relative rotation of a pair of arms as the arms approach a door-open limit position, and which aids the door closer in moving the door from the door-open limit position.

Door closer assist linkage

A hydraulic door closer is provided with a fluid seal for its output shaft, the seal comprising multiple O-rings disposed side-by-side in an elongated annular chamber.

Hydraulic door closer construction

Hydraulic door closer apparatus comprises a cylinder and an elongated piston disposed in the cylinder, the piston being made of relatively easily machined material, but having associated with it a rack of harder, wear and impact-resistant material for transmitting forces and motion to and from the piston.

Growing community of inventors

Lancaster, PA, United States of America

Sidney Lieberman