Patent ID: 8806715

Claim:
A door closer having at least one of a locking function and a free-swing function, comprising: a door closer housing; an output shaft configured to be connected to a door; a piston assembly connected to the output shaft and guided in the door closer housing; a closer spring; a piston rod that connects the piston assembly to the closer spring; a hydraulic lock compartment adapted to lock the closer spring; an sliding-coupling accommodating space for the closer spring that becomes smaller during an opening process of the door; a spring-loaded check valve that locks toward the accommodating space becoming smaller and arranged between the hydraulic lock compartment and the accommodating space; a closer spring tension piston guided in the door closer housing and abutting on the closer spring; wherein the spring-loaded check valve is arranged such that hydraulic oil in the accommodating space is pre-pressurized by an opening process and is actively pumped through the spring-loaded check valve into the hydraulic lock compartment.