PURPOSE: To easily equalize the initial tensions of wires by engaging the corresponding end wires of a pair of wire pulley devices on 2 pairs of fixed pulleys to form a common wire, and installing a stopper for fixing the initial position of a carriage.

CONSTITUTION: The wires A, B of wire pulley devices 9A, 9B are made common, 2 pairs of fixed pulleys 17A and 17B, 18A and 18B are arranged facing each other in the lateral direction of a half-speed carriage 6, and both ends of wires A, B are engaged on these pulleys to form freely movable common parts of wires C1, C2. Both sides 6a, 6b of the carriage 6 are in soft contact with the stoppers 20A, 20B of the fixed part of a device. Therefore, the carriage 6 corrected in posture each time it returns to the initial position and it moves always in the same posture, even after repeated reciprocations.