Patent ID: 9410352
Filing Date: 2016-08-09
CPC Classification: E05F,E05Y,Y10T

Claim Text:
1. A door closer comprising: a housing which is fixed to a door; a link of which one end is connected to a door frame; a link shaft which is inserted into the housing, of which an upper end projecting to the outside of the housing is connected to the other end of the link, and which is elastically pressurized to rotate in a direction that the door is closed; and a power adding unit which adds power to close the door, wherein the power adding unit comprises a cam which coaxially rotates with the link shaft in the housing and a cam pusher which is elastically pressurized to be in close contact with the outer circumferential surface of the cam, wherein the outer circumferential surface of the cam comprises an arc surface portion which is spaced apart an equal distance from the rotation axis of the cam, a concave surface portion which is spaced apart a distance shorter than the arc surface portion from the rotation axis of the cam, and a pair of projection corner portions which connect the arc surface portion and the concave surface portion, wherein when the outer circumferential surface of the cam, with which the cam pusher comes into contact, is switched from the arc surface portion to the concave surface portion as the cam rotates, the rotation force of the link shaft is increased by the elastic pressing force of the cam pusher, and wherein the door closer further comprises: a pinion gear which coaxially rotates with the link shaft; a piston which extends in the longitudinal direction of the housing, is inserted into the housing to reciprocate in the longitudinal direction of the housing, and comprises a rack gear portion which is formed on one end thereof and engaged with the pinion gear; and a first coil spring which elastically pressurizes the piston such that the link shaft rotates in a direction that closes the door.