Maxson Automatic Machinery Company (Westerly RI USA) incorporates a proportional type tension control system into its roll stand design to allow for automatic brake compensation as the roll decreases in diameter. The device eliminates the need to thread the web through load cell tensioning rolls or dancer roll type mechanisms, while still providing the same level of precise web tautness that is required for accurate cut offs on a sheeter. The simplicity of the design lends itself to being retrofitted to existing roll stand installations.
The system includes a tension controller, an air filter, an electronic-pneumatic converter, a sensor collar, and a proximity sensor. The sensor mounts on the roll stand’ s arm and monitors the number of rotations, detecting the proximity of the sensor collar. This signal is fed to the tension controller, which reduces the diameter. For the maximum roll diameter, the controller sends the maximum output of 10 volts to the electro - pneumatic (E-P) converter. As the roll diameter reduces, the voltage lessens proportionately. The E-P converter translates the voltage to a pneumatic output - air pressure. As the voltage decreases, the air pressure fed to the roll stand brakes is reduced. The change in air pressure can be monitored by the pressure gauge.
An added feature of this design is the ability of the tension controller to monitor a preset “low roll” diameter condition. When a “low roll” diameter is reached, a signal is sent to the sheeter drive to slow down to a minimum line speed.