| 摘要 |
PURPOSE:To ensure safety of a device in use, by providing a restraining mechanism, permitting placing and removing of a key only when a shut-off valve is operated to a closed position, between a changeover operation mechanism and the key. CONSTITUTION:A gap 21, for a protruded part 5b to be located in a retracted position under a condition inserted with a key as prescribed, is formed between an internal end surfaces of a key hole 19 and end surface of a rotary cam 18, at a face-to-face position to the internal end surface. A restraining mechanism 7 consists of the protruded part 5b, grooved part 19b and gap 12, when a shut- off valve 3 operates as a normal safety valve by inserting rotation of a key 5, insertion and removal of the key 6 is inhibited, further only under a condition for the shut off valve 3 to be operated to a closed position by the rotation of the key 5, removal and insertion of the key 5 are permitted, then safety of a device in use can be ensured. |
