Door lock with reinforced fireproof function

A door lock comprising:

• an inner chassis made of ferrous material or stainless steel, wherein the inner chassis includes a first groove formed on an outer periphery thereof,
• an inner mounting seat coupled to the inner chassis and including a second groove aligned with the first groove along an axis parallel to a longitudinal axis of the inner chassis;
• an outer chassis made of ferrous material or stainless steel;
• an outer mounting seat coupled to the outer chassis, wherein the outer mounting seat includes an opening aligned with the first and second grooves along the axis parallel to the longitudinal axis of the inner chassis, wherein the outer mounting seat is coupled to the inner mounting seat, wherein the inner and outer mounting seats are configured to be received in a first through-hole of a door, and wherein the inner and outer chassis are respectively at an inner side and an outer side of the door, with the first through-hole of the door extending from the inner side through the outer side of the door;
• a retractor movably received between the inner and outer mounting seats, wherein the retractor includes an engaging portion received in the opening, wherein the engaging portion is operatively connected to a latch device;
• an inner fixing member made of ferrous material or stainless steel and coupled to the inner chassis, wherein the inner fixing member is configured to be fixed to the inner side of the door;
• an outer fixing member made of ferrous material or stainless steel and coupled to the outer chassis, wherein the outer fixing member is configured to be fixed to the outer side of the door and closes the first through-hole;
• an inner operating unit coupled to the inner fixing member and including an inner handle operatively connected to the retractor;
• an outer operating unit coupled to the outer fixing member and including an outer handle operatively connected to the retractor;
• and
• a cover made of ferrous material or stainless material, wherein the cover is coupled to and abuts a face of the inner fixing member, and wherein the cover includes an insertion portion that closes the first groove,
• wherein melting points of the inner chassis, the outer chassis, the inner fixing member, the outer fixing member, and the cover are higher than melting points of remaining components of the door lock,
• wherein when the remaining components of the door lock melt under a fire occurred at one of the inner and outer sides of the door, the inner chassis, the outer chassis, the inner fixing member, the outer fixing member, and the cover do not melt, the inner chassis, the outer chassis, the inner fixing member, and the outer fixing member still close the first through-hole of the door, and the insertion portion of the cover closes gaps between the first and second grooves and the first through-hole of the door, impeding spread of flame or smoke caused by the fire from the one of the inner and outer sides of the door to another of the inner and outer sides of the door, thereby slowing down spread of the fire.