PURPOSE: To maintain a no-contact and no-noise state and optionally move a power line depending on the location of a track, providing a lock-up mechanism which automatically performs locking-up in a prescribed position when a support beam for a current collector is displaced by swinging.
CONSTITUTION: A mount 38 is provided beside a vehicle position in a tunnel so that the mount extends downward. A strut 40 projects from the mount 38. An unlocking rail 41 is attached to the strut 40. An unlocking wheel 42 is so supported by an arm 43 swingable supported at one end on a pin 44 that the wheel 42 can roll on the rail 41. The other end of the arm 43 is coupled to a link 45, which is coupled to a hook 47 swingable supported by a pin 48 on a support beam 31 for a current collector. When the wheel 42 is not thrusted by the rail 41, the hook 47 is engaged with a latch 49 on a frame 10 to lock up the clockwise swing of the support beam 31 due to a spring 33.