Novel cam action hydraulic door closer

A novel cam action hydraulic door closer comprising:

• a door closer housing, the door closer housing being provided therein along an axis direction thereof with an inner chamber filled with hydraulic oil;
• a bidirectional piston, the bidirectional piston being movably inserted in the inner chamber and partitioning the inner chamber into a main shaft chamber and a spring chamber;
• a transmission camshaft, an axial direction of the transmission camshaft being perpendicular to an extending direction of the door closer housing, at the same time the transmission camshaft being pivoted in the door closer housing and accommodated in the main shaft chamber;
• and
• a drive spring, the drive spring being accommodated in the spring chamber, two ends of the drive spring being abutted against the bidirectional piston and the door closer housing respectively, the drive spring being configured to drive the bidirectional piston to be abutted and pressed on the transmission camshaft;
• wherein the bidirectional piston is provided therethrough with a fluid channel communicating with the main shaft chamber and the spring chamber, and an overload valve is installed in the fluid channel;
• the overload valve is configured in a way that if pressure in the main shaft chamber exceeds a threshold pressure, the overload valve allows the hydraulic oil to flow between the main shaft chamber and the spring chamber.