Patent ID: 8336598

Claim:
A safety device for a roller blind comprising: a housing in which being disposed a driven mechanism extending to both ends of the housing, the driven mechanism having one end formed with a polygonal concave, the housing being formed around the concave with an assembling portion which is formed with two slide grooves at two opposite sides thereof, and a locking hole being formed in a periphery of the concave and located between the two slide grooves; a locking member assembled on the assembling portion of the housing and formed with an assembling hole to be aligned with the concave, around an inner surface of the assembling hole of the locking member being formed a flange which is located adjacent to the housing, the locking member being formed with two slide blocks at two opposite sides of the assembling hole, a locking block to be engaged in the locking hole, and the locking block including a locking portion extending toward the locking hole, around the assembling hole and adjacent the locking block being formed an assembling block, and around the assembling hole and opposite to the assembling block being formed a connecting block, the two slide blocks being received in the slide grooves, and the locking portion of the locking block being engaged with the locking hole; a drive mechanism including a driven member, a bead chain and a drive member, the driven member being a cylindrical structure received in the assembling hole and abutted against the flange, the driven member being formed with a through hole to be aligned with the assembling hole, in an inner surface of the through hole being formed three spaced locking grooves, and around an outer surface of the driven member being formed a stop flange and a plurality of bead grooves equidistantly formed around the stop flange, the bead chain including a plurality of beads connected together and being hung to the driven member in such a manner the beads are engaged in the bead grooves, the drive member being a hollow cylindrical structure received in the through hole and having one end formed with a polygonal conical protrusion inserted through the assembling hole and into the concave of the housing and having another end formed with a chamber, the drive member being formed around its outer surface with three ribs to be engaged with the locking grooves of the through hole; an elastic member received in the chamber of the drive member; and a cover formed with a positioning concave and fixed to the assembling block and the connecting block of the locking member, and the elastic member being received between the chamber of the drive member and the positioning concave.