US Patent 7930916 Locking device and key

There is disclosed a key required to have a reduced mechanical strength. When an authentic key is inserted into the keyway in a locking device, only a plunger member starts to move from a standby position toward an operative position. When the plunger member is pushed to the operative position, an operating lever located in the locked position swings to the unlocked position. The operating lever unlocks a locking mechanism that is in a locked state. When an inauthentic key is inserted in the keyway, the plunger member and sleeve member move together to the operative position. The operating lever in the locked position does not swing. Thus, the operating lever maintains the body portion of the locking mechanism locked.