hydraulic door closer

Have you ever thought how this stuff works??
 

yeah i have you the answer for you!!!!

Hydraulic door closer are some devices that are installed at the top of the door and its frame. A hydraulic door closer helps close a door automatically. 

Working of the Hydraulic Door Closers:-

The hydraulic door closer is simple and easy to work with. One end of the hydraulic door is attached to the door, and the other end is attached to the door frame. When the door is opened, the hydraulic door closer pulls the door and closes it rather than slamming the door. This happens because the closer has a sealed tube which contains a spring, so that the closer can work properly like how it is supposed to work. It includes a fluid-filled chamber which releases the pressure to close the door in a slow manner rather than banging it. Moreover, the door closer even helps in improving the energy efficiency, in case of any unexpected accident such as fire.