Door lock mechanism with a release button

A door lock mechanism, comprising:

• a retainer housing assembly comprising:
• a retainer housing adapted to be mounted to a doorframe and including a retaining slot defined in a lateral side thereof and a compartment defined therein, a lock core received in the compartment the lock core having a retaining member mounted to a lower end thereof, and a first elastic member mounted around the retaining member;
• a lock piece pivotally received in the retaining slot and including an arcuate operative surface, the lock piece further including a first end releasably engaged with the retaining member and a second end;
• a second elastic means for returning the lock piece to its initial position;
• and
• a release button having a first end releasably engaged with the second end of the lock piece and a second end for manual operation so as to be moved between a first position which engages with the lock piece and a second position which disengages from the lock piece;
• and
• a chain housing assembly comprising:
• a chain housing having a longitudinal compartment defined therein;
• a chain received in the longitudinal compartment of the chain housing and including a first end fixedly mounted to the chain housing and a second end which is stretchable beyond the chain housing;
• a third elastic means mounted around the chain for returning the chain to its initial unstretched position;
• and
• a slide bolt securely mounted to the second end of the chain and releasably, slidably received in the retaining slot of the retainer housing;
• wherein when in a locked position and when the release button is in its first position, the lock piece is stopped by the retaining member and the slide bolt is retained in the retaining slot and allows the door to be opened for a small gap, and when in a locked position and when the release button is in its second position, the lock piece is disengaged from the lock piece and thus allows removal of the slide bolt from the retaining slot without operation of the lock core.