Methods and mechanism for providing variable torque with variable torque resolution to rotation of a web roll

Abstract

A mechanism (C) for tensioning a web extending from a rotating roll (R) includes three fluid relays ( 200 - 202 ) and two amplifiers ( 204, 205 ). A variable pressure pilot signal (P) drives a piston ( 66 ) of a rotational control apparatus (A) to create a pilot torque to the rotating roll (R). In the event that the variable pressure pilot signal (P) exceeds the bias pressures (B 1 -B 3 ) of the fluid relays ( 200 - 202 ), the pistons ( 64, 68, 70, 72 and 74 ) are driven by fluid relays ( 200 - 202 ) to create relay torques to the rotating roll (R) in addition to the pilot torque in direct proportion to differences between the variable pressure pilot signal (P) and the bias pressures (B 1 -B 3 ). The relay torques created by the second and third relays ( 201, 202 ) are amplified by the amplifiers ( 204, 205 ). Thus, the rotational control apparatus (A) can be fully utilized for its full torque range while still providing enough resolution to control tension of the web (W) precisely.

1 . Method for controlling rotation comprising: 
 receiving a variable pilot signal and providing a pilot torque to the rotation in direct proportion to the variable pilot signal;    actuating a first relay when the variable pilot signal is above a first level and providing a first relay torque to the rotation in addition to the pilot torque, with the first relay torque being in direct proportion to a first difference between the variable pilot signal and the first level; and    amplifying the first relay torque provided by the first relay.    
     
     
         2 . The method of  claim 1  further comprising: 
 actuating a second relay when the variable pilot signal is above a second level and providing a second relay torque to the rotation in addition to the pilot torque and the first relay torque, with the second relay torque being in direct proportion to a second difference between the variable pilot signal and the second level.  
 
     
     
         3 . The method of  claim 2  further comprising: 
 amplifying the second relay torque provided by the second relay, with the first level being different than the second level, with the second relay torque being amplified at a different degree than the first relay torque.  
 
     
     
         4 . The method of  claim 3  further comprising: 
 actuating a third relay when the variable pilot signal is above a third level and providing a third relay torque to the rotation in addition to the pilot torque, the first relay torque, and the second relay torque, with the third relay torque being in direct proportion to a third difference between the variable pilot signal and the third level, with the third level being less than the first and second levels.  
 
     
     
         5 . The method of  claim 4  with receiving the variable pilot signal comprising receiving the variable pilot signal in the form of a variable pressure pilot signal.  
     
     
         6 . Mechanism for controlling rotation comprising, in combination: 
 means for receiving a variable pilot signal, with the variable pilot signal adapted to cause a pilot torque to the rotation in direct proportion to the variable pilot signal;    a first relay receiving the variable pilot signal and creating a first relay signal in direct proportion to a first difference between the variable pilot signal and a first level, with the first relay signal adapted to cause a first relay torque to the rotation in addition to the pilot torque, with the first relay torque being in direct proportion to the first difference; and    a first amplifier amplifying the first relay signal.    
     
     
         7 . The mechanism of  claim 6  further comprising, in combination: 
 a second relay receiving the variable pilot signal and creating a second relay signal in direct proportion to a second difference between the variable pilot signal and a second level, with the second relay signal adapted to cause a second relay torque to the rotation in addition to the pilot torque and the first relay torque, with the second relay torque being in direct proportion to the second difference.  
 
     
     
         8 . The mechanism of  claim 7  further comprising, in combination: 
 a second amplifier amplifying the second relay signal, with the first level being different than the first level, with the second relay signal being amplified by the second amplifier at a different degree than the first relay signal is amplified by the first amplifier.  
 
     
     
         9 . The mechanism of  claim 8  further comprising, in combination: 
 a third relay receiving the variable pilot signal and creating a third relay signal in direct proportion to a third difference between the variable pilot signal and a third level, with the third relay signal adapted to cause a third relay torque to the rotation in addition to the pilot torque, the first relay torque and the second relay torque, with the third relay torque being in direct proportion to the third difference, with the third level being less than the first and second levels.  
 
     
     
         10 . The mechanism of  claim 9  with the receiving means comprising means for receiving a variable pressure pilot signal.  
     
     
         11 . Method for tensioning a web comprising: 
 rotating a roll of the web;    applying a pilot torque to the rotation of the roll in direct proportion to a variable pilot signal to create tension in the web extending from the roll; and    applying a first torque to the rotation of the roll in addition to the pilot torque, with the first torque being in direct proportion to a first difference between the variable pilot signal and a first level, with the first level being greater than zero, with applying the first torque comprising automatically applying the first torque to the rotation of the roll whenever the variable pilot signal is greater than the first level, with the tension in the web extending from the roll being the combination of the pilot torque and the first torque.    
     
     
         12 . The method of  claim 11  with the applying the first torque comprising applying the first torque to the rotation of the roll in direct proportion to a first amplitude of the first difference, with the first amplitude being greater than one.  
     
     
         13 . The method of  claim 12  further comprising: 
 applying a second torque to the rotation of the roll in addition to the pilot torque and the first torque, with the second torque being in direct proportion to a second difference between the variable pilot signal and a second level, with the second level being greater than zero, with the tension in the web extending from the roll being the combination of the pilot torque, the first torque and the second torque.  
 
     
     
         14 . The method of  claim 13  with applying the second torque comprising applying the second torque to the rotation of the roll in direct proportion to a second amplitude of the second difference, with the second amplitude being greater than one, with the second amplitude being different than the first amplitude.  
     
     
         15 . The method of  claim 14  with the second level being different than the first level.  
     
     
         16 . The method of  claim 15  further comprising: 
 applying a third torque to the rotation of the roll in addition to the pilot torque, the first torque and the second torque, with the third torque being in direct proportion to a third difference between the variable pilot signal and a third level, with the third level being greater than zero, with the tension in the web extending from the roll being the combination of the pilot torque, the first torque, the second torque and the third torque.  
 
     
     
         17 . The method of  claim 16  with the third level being different from the second level and from the first level.  
     
     
         18 . The method of  claim 13  with applying the second torque comprising applying the second torque to the rotation of the roll in direct proportion to a second amplitude of the second difference, with the second amplitude being greater than one, with the second level being different than the first level.  
     
     
         19 . The method of  claim 11  further comprising: 
 applying a second torque to the rotation of the roll in addition to the pilot torque and the first torque, with the second torque being in direct proportion to a second difference between the variable pilot signal and a second level, with the second level being greater than zero, with the tension in the web extending from the roll being the combination of the pilot torque, the first torque and the second torque.  
 
     
     
         20 . The method of  claim 19  further comprising: 
 applying a third torque to the rotation of the roll in addition to the pilot torque, the first torque and the second torque, with the third torque being in direct proportion to a third difference between the variable pilot signal and a third level, with the third level being greater than zero, with the tension in the web extending from the roll being the combination of the pilot torque, the first torque, the second torque and the third torque.  
 
     
     
         21 . Mechanism for tensioning a web extending from a rotating roll comprising, in combination: 
 means for receiving a variable pressure pilot signal, with the variable pressure pilot signal adapted to cause a pilot torque to the rotating roll in direct proportion to the variable pressure pilot signal; and    a fluid relay having an actuator, an inlet and an outlet, with the actuator receiving the variable pressure pilot signal, with the inlet being connected to a constant supply pressure, with the outlet adapted to cause a first relay torque to the rotating roll in addition to the pilot torque, with the first relay torque being in direct proportion to an outlet pressure, with the outlet pressure of the fluid relay being related to a difference between the variable pressure pilot signal and a first pressure, with the first pressure being greater than zero.