Patent ID: 6854161

Claim:
An apparatus for opening and closing a door, comprising a hydraulic hinge including a rotary member and a fixed member; wherein the rotary member includes: a first housing adapted to fix to one side of a door; a piston guide placed inside the first housing; a rotary shaft disposed inside the piston guide and fixed to the first housing so that the rotary shaft rotates when the door is opened and closed; and a piston screwed with the rotary shaft to be rotatably elevated along the piston guide when the rotary shaft rotates; wherein the fixed member includes: a second housing adapted to fix to one side of a doorframe and screwed with the piston guide; a cylinder placed inside the second housing and having an oil outlet penetrating the cylinder for allowing oil to pass through the oil outlet; a head mounted on a top surface of the cylinder; an adjusting bolt screwed with the head such that an oil circulating passage is formed in the fixed member for adjusting an amount of oil outflow; and an outflow part formed on the top surface of the cylinder and having a plurality of support protrusions formed on the outflow part for allowing the oil outlet to communicate with the oil circulating passage.