| 摘要 |
The device is composed of a drive roller 6 driven by means of an AC gear motor 16 which is governed by a control loop b of the actual web 3, established between said roller 6 and the end of a rotary arm 8, balanced and of adjustable length, the shaft 18 of which actuates a highly sensitive potentiometer so that the difference between its output voltage and a preset reference voltage, suitably amplified, is applied to a frequency variator which in turn modifies the speed of the gear motor 16, compensating for the increase or decrease in the length of the control loop b. It is applicable to the packaging industry. <IMAGE>
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