Door lock position indicating key - has two parts rotated as lock is operated, showing marks indicating open or shut

摘要

The key for a door lock carries a fitting which visually indicates if the lock has been opened or closed. The finger grip (2) has a stepped stem (4) which fits into the ward (1) which has a boss (6) at the junction point, so that one can rotate inside the other. The boss has an opening (14) through it, and the larger dia. part of the stem carries a red and a green marking, indicating whether the lock is open or shut. This is visible through the opening. The green mark indicates closed, and the red mark indicates shut. The effort required to rotate the stem in the boss is less than that required to turn the lock. Other designs include an with a spring between the two parts.