Safety locking mechanism for lockset

A safety locking mechanism for a lockset, having a cover plate and a lock body, comprising:

• a locking push rod having a direction-limiting shaft and a cylindrical rod, wherein the direction-limiting shaft is mounted at a first end of the cylindrical rod, the cylindrical rod defines a helical inclined surface at a adjacent to the direction-limiting shaft, the helical inclined surface protruding from the cylindrical rod and axially extending along the surface of the cylindrical rod, and a second end of the cylindrical rod presses against the cover plate of the lockset;
• a locking stopper defines a specially-shaped hole, wherein the specially-shaped hole includes a space having a cross-section similar to the cross-section of the helical inclined surface such that the helical inclined surface section of the locking push rod fits into the specially-shaped hole, the locking stopper is rotatably mounted on the cylindrical rod, a front end of the helical inclined surface is inserted into the specially-shaped hole, and when axially moving in the specially-shaped hole, the helical inclined surface drives the locking stopper to rotate only in a radial direction,
• wherein the lock body comprises a lock tongue for locking and unlocking the lockset, a locking shaft for providing the safety lock mechanism to the lockset by locking the lock tongue when the cover plate is removed, and the lock body defines a direction-limiting groove having the same cross-sectional shape as the direction-limiting shaft, the direction-limiting shaft is fitted in the direction-limiting groove allowing the direction-limiting shaft to be slidable in the direction-limiting groove only in an axial direction, and a locking compression spring is mounted between the direction-limiting shaft and a bottom end of the direction-limiting groove in a compressed manner to elevate the locking push rod, rotate the locking stopper and lock the lock tongue when the cover plate is removed.