US Patent 9982457 Anti-theft device for door locks

The anti-theft device is configured in a door lock, and contains a first blocking piece, a second blocking device, a positioning piece, and a lever. The first blocking piece contains a first section and a second section bended and extended perpendicularly from the first section. The first section has a first through hole and a second through hole. The lever is engaged by a lock heart of the door lock. When the door lock is locked, the lock heart is turned to engage the lever so that the lever drives the first blocking piece downward by its first through hole. The second section of the first blocking piece as such blocks a lock tongue of the door lock so that the door lock cannot be opened without using key.