トラップト・キー・インタロックの安全機能要件に関する考察(機械要素,潤滑,設計,生産加工,生産システムなど)  [in Japanese] Consideration on the Requirements of Safety Function for Trapped Key Interlock(Machine Elements, Design and Manufacturing)  [in Japanese]

"Trapped key interlock" is an alternative to "lockout" for controlling hazardous energy in order to protect the machine maintenance personnel working at any place where they could be injured by the unexpected release of hazardous energy. In view of the above, this paper proposes that the relation of "locking up the power switch in the OFF position," "picking up the key for hostage control" and "unlocking the movable guard for accessing to the working area" should be made unite in terms of system by applying the "principle of safety confirmation" to the "trapped key interlock." The points in designing such unite system are that the movable guard should be unable to be opened unless the key for hostage control is picked up by the machine maintenance personnel and that the key for hostage control should be unable to be inserted into the key hole unless the movable guard is closed. To realize these points, this paper formulates these interrelations, presents them in the form of interlock structure and shows an example of configuration that can meet the required safety functions.