Last Updated on May 30, 2024
Door closers work by balancing two forces. The first force is a spring, which wants to pull the door back into a closed position. The second force is hydraulic fluid. It is used to dampen the motion of the spring to prevent slamming.
Refer to our article: How to Adjust a Door Closer if you’d like to adjust your closer.
Function of the Door Closer Spring
The spring in a door closer acts to pull the door closed. When the door is open, the spring is stretched and pulling on the door in an attempt to close it. By itself, it can accomplish the goal, however by itself it would also result in the door getting slammed into the frame with excessive force. This would inflict damage to the door, the frame, the locks, or any fingers that may be in the way!
To balance this force and prevent the door closer from slamming shut, a system of hydraulic fluid is used.
How Door Closer Hydraulic Oil Works
Inside a door closer there are chambers filled with hydraulic fluid.
When the door is opened, a check valve opens that allows the closer fluid to rush into a far chamber with practically no resistance at all. Very quickly.
But for the door to close, the fluid needs to return back to it’s starting chamber. The initial check valve won’t let the fluid return back the way it came; instead, the fluid must navigate through restricted chambers or tubing, with much smaller openings.
When adjusting a door closer, you are adjusting the flow of the oil through the closer. If you allow the fluid to go through the system more quickly by loosing the adjustment screws, the door closing/latching speed will be quicker. If you restrict the flow of the fluid by tightening the adjustment screws, the door will close/latch more slowly.
This basic method has been used in door closers for over 100 years. While it is a simple concept, various adaptations to the principles allow for additional door closer features which have uses in different applications. Whether you have a very basic or a very complex model, they are designed so you can adjust a door closer for optimal performance.
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