Tension control device for paper web in a rotary printing machine

In a rotary printing machine which includes a plurality of web-feeds each of which is provided with a paper roll (3, 4, 5) and a brake mechanism (6, 7, 8) whose braking force can vary in response to fluid pressure supplied from a pressure source (16) and which can succeedingly perform splicing to a new roll (4, 5 or 3) when a preceding roll (3, 4 or 5) reaches to a predetermined remain level,

• a tension control device comprising;
• a tension detecting mechanism (A) including a floating roller (11) for guiding paper web (9) fed from one of the rolls (3, 4, 5), a single arm (14) one end of which is pivotally supported by a pivot (13) so as to move said arm (14) angularly and the other end of which supports said floating roller (11) rotatable, and a force applying means for applying a constant force to said single arm (14) against the tension applied to said paper web (9) so that said single arm (14) can be moved angularly in response to the magnitude of the tension applied to the paper web (9);
• a fluid pressure feeding conduit system (B) including at least three upper conduits, a first upper conduit (18a), a second upper conduit (18b), and a third upper conduit (18c) for feeding fluids having respective different pressures towards a lower conduit (18z) connected to the above mentioned brake mechanisms (6, 7, 8) associated with the above mentioned paper rolls (3, 4, 5);
• a first brake-force adjusting mechanism (C) associated with the above mentioned first upper conduit (18a) to make the output pressure out of this brake-force adjusting mechanism (C) be a first pressure which is reduced as the tension applied to the paper web (9) increases;
• a second brake-force adjusting mechanism (D) associated with the above mentioned second upper conduit (18b) to make the output pressure out of this brake-force adjusting mechanism (D) be a second pressure which is reduced as the tension applied to the paper web (9) increases and is greater than the above mentioned first pressure with respect to the same tension as the above;
• a first switching mechanism (E) arranged among the above mentioned first upper conduit (18a), the above mentioned second upper conduit (18b), and the above mentioned lower conduit (18z), to switch in response to one of predetermined emergency signals from said first upper conduit (18a) to said second upper conduit (18b) to communicate between said second upper conduit (18b) and said lower conduit (18z);
• and
• a second switching mechanism (F) arranged between the above mentioned lower conduit (18z) and the above mentioned third upper conduit (18c) for feeding a third pressure greater than the maximum of the second pressure, said second switching mechanism (F) being located lower than the above mentioned first switching mechanism (E), and actuated in response to a splicing operation signal to make the connection between said third upper conduit (18c) and said lower conduit (18z) available for only a predetermined period.