Rack & Pinion Technology
This technology is used on Yale doors closer ranges. When a door arm is pulled, a pinion rotates and engages its teeth with the rack's teeth in a piston. This drives the piston down the cylindrical bore and compresses its spring lying inside. The energy stored during the opening of the door is released by the spring when the door is left / let go to close the door. The speed of the door and latching can be controlled by the hydraulic fluid valves available.