A door closer is a mechanical device that closes a door, in general after someone opens it, or after it was automatically opened
A manual door closer stores the energy used in the opening of the door and releases it to close the door. To limit the speed at which the door closes, common door closers use hydraulic (oil-filled) dampers, although spring mechanisms may also be used. The speed at which the door closer closes the door may be adjustable by up to two set screws. These screws often adjust the sweep speed and the latch speed of the door. The latch speed is the speed that the door travels in the last third to 10 degrees as it closes and is often set fast so that the door can properly latch closed. The sweep speed is the speed which the door travels at along the first two thirds of its travel and is often set slower than the latch speed. Door closers which provide this two-stage action and close doors at a determined rate are called ‘controlled’ door closers.
