Lock mechanism for stage apparatus

A lock mechanism for a stage apparatus, said stage apparatus having a stationary support board and a movable stage which is relatively movable in a plane parallel to said stationary support board, comprising:

• a pair of engaging members which project from a surface of said movable stage;
• a rotational lock device including a pair of arm members rotatably mounted at center portions thereof on a common rotational shaft so that said arm members are relatively rotatable to each other, wherein said arm members are rotatable between an engaged position at which one and the other pairs of facing free ends of said arm members clasp corresponding one and the other said engaging members, and a disengaged position at which said one and the other of said pairs of facing free ends of said arm members move away from said corresponding one and the other said engaging members;
• a lock driving device which rotates said arm members to said engaged position upon said movable stage entering a non-operational state;
• and
• an unlock driving device which rotates said arm members to said disengaged position so that said movable stage enters an operational state.