PURPOSE:To provide high precise tension, by a method wherein a dancer roller employing a linear actuator is situated between a drum, unwinding a linear or beltform material, and a drum, winding the wire material with the aid of a variable speed electric motor, to control the tension of the wire material. CONSTITUTION:An electric wire 1 is wound around a drum 9, driven by a D.C. electric motor 8, through a line pulley 4, a dancer roller 5, a line pulley 6, and a wire speed detector 7 by means of an unwinding drum 3 driven by a D.C. electric motor 2. A servo amplifier 10 controls the electric motor 8 by means of an instruction by which a speed is set at 11. By means of an output from a tension setter 22, a constant current is generated at 21, an actuator for a dancer roller 5 is driven to move a roller 5 in the direction of an arrow mark. From a deviation amount of the actuator and a wire speed detected by the wired speed detector 7, an unwinding speed is computed at 19 to control running of the motor 2 by means of 20. This constitution enables the tension of the electric wire 1 to be precisely regulated to a given value.
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