Patent ID: 7788768

Claim:
A door closer, comprising: a closer that includes a pinion that rotates in the forward and reverse directions together due to the opening and closing, respectively, of a door, a cylinder that is meshed with the pinion and moves forward and backward, and a closing spring that, via the cylinder and the pinion, provides force that is used to close the door, and an opening-assistance device that includes an opening spring that stores a door-opening force due to the rotation of said pinion when the door is opened, a locking mechanism that locks the opening spring in the opening-force-storing condition when the door is opened, and an unlocking mechanism that unlocks the locking mechanism when the door is closed, and wherein said closer and said opening-assistance device are inside a same case so that the functioning of said closer and that of said opening-assistance device are interlinked when the door is opened, and wherein said opening-assistance device comprises said opening spring, said locking mechanism, said unlocking mechanism, a fixing member that extends along the moving direction of said cylinder under a fixed condition at one end of said case, and a moving member that receives the force of said opening spring, that can make contact with said cylinder, and that moves along the fixing member due to the moving force between itself and the cylinder, and wherein said locking mechanism has locking balls that lock the movement of the moving member when the door is opened and lock the opening spring in an opening-force-storing condition, and due to the closing of the door, said moving member releases the locking balls' locking of the movement of the moving member.