PURPOSE: To control a belt tension at an appropriate value, by a method wherein a water amount of a water tank connected to a belt and a snap pulley is regulated according to the number of revolutions of a driven pulley.
CONSTITUTION: A rotation speed of a driven pulley 3 changes according to a transportation amount, a friction factor μ between a drive pulley 1 and a belt 2, etc., provided the tension is constant. For example, as the friction factor μ decreases, the rotation speed reduces. Therefore, the weight of a water tank which is suspended from a weight 8 of a take-up device 22 is adjusted corresponding to the rotation speed, i.e., in a manner to switch electromagnetic valves 11 and 12 located at a pouring port and a drainage port, repsectively. The permits to obtain an appropriate belt tension at all times irrespective of changes in the friction factor.
TANIYOSHI SHIYUUICHI
ITOU MASAHIRO
