Press and method of controlling the press

Abstract

A press for processing a web and a method of controlling a press. The press includes at least one nip having a first press roll and a second press roll. A first belt runs through the at least one nip. A second belt runs through the at least one nip. A sandwich stretch is formed by the first and second belts and is arranged after the at least one nip. A first mechanism is provided for driving the first belt. A second mechanism is provided for driving the second belt. The method includes driving the first belt at a first speed, and driving the second belt at a second speed, wherein the first speed is substantially the same as the second speed at least in a region of the sandwich stretch.

What is claimed:  
     
         1 . A press for processing a web comprising: 
 a first press roll and a second press roll arranged to form at least one nip;    a first belt running through the at least one nip;    a second belt running through the at least one nip;    a sandwich stretch formed by the first and second belts being arranged after the at least one nip; and    a first mechanism for driving the first belt; and    a second mechanism for driving the second belt.    
     
     
         2 . The press of  claim 1 , wherein the at least one nip allows the first belt, the second belt and the web disposed therebetween to travel therethrough.  
     
     
         3 . The press of  claim 1 , wherein each of the first and second mechanisms are arranged after the at least one nip.  
     
     
         4 . The press of  claim 1 , wherein the web comprises one of a paper web, a cardboard web, a tissue web, and a fibrous material web.  
     
     
         5 . The press of  claim 1 , wherein the at least one nip comprises an extended nip.  
     
     
         6 . The press of  claim 1 , wherein the first press roll comprises a shoe press roll and wherein the second press roll comprises a cylindrical mating roll.  
     
     
         7 . The press of  claim 1 , wherein at least one of the first and second belts comprises an air-permeable water-absorbent press felt.  
     
     
         8 . The press of  claim 1 , wherein the first mechanism comprises a first guide roll and wherein the second mechanism comprises a second guide roll.  
     
     
         9 . The press of  claim 1 , wherein the first belt is guided away from each of the web and the second belt after the sandwich stretch.  
     
     
         10 . The press of  claim 9 , wherein the first mechanism comprises a driven following guide roll that guides away the first belt.  
     
     
         11 . The press of  claim 1 , wherein the second belt is adapted to guide the web alone after the sandwich stretch.  
     
     
         12 . The press of  claim 1 , wherein the second mechanism comprises a driven guide roll that guides away the web and the second belt.  
     
     
         13 . The press of  claim 12 , wherein the second belt comprises an air-permeable water-absorbent press felt and wherein the driven guide roll is suctioned.  
     
     
         14 . The press of  claim 1 , wherein the second belt comprises at least one of a non-water absorbent belt, a slightly water-absorbent belt, and a non-air-permeable transfer belt and a slightly air-permeable transfer belt.  
     
     
         15 . The press of  claim 1 , wherein the second belt comprises at least one of an air-permeable press felt and a water-absorbent press felt.  
     
     
         16 . The press of  claim 15 , wherein the second belt is guided, after the sandwich stretch, over at least one of a fixed guide element and a suctioned guide element.  
     
     
         17 . The press of  claim 1 , wherein the second mechanism comprises at least one of a fixed guide element and a suctioned guide element.  
     
     
         18 . The press of  claim 1 , further comprising a take-up element arranged after the sandwich stretch, wherein the second belt is adapted to transfer the web to the take-up element.  
     
     
         19 . The press of  claim 18 , wherein the take-up element comprises a third belt.  
     
     
         20 . The press of  claim 19 , further comprising a driven guide roll arranged downstream the take-up element, wherein the second belt is adapted to transfer the web to the take-up element and thereafter be guided by the driven guide roll.  
     
     
         21 . The press of  claim 1 , further comprising a control unit coupled to the first and second mechanisms.  
     
     
         22 . The press of  claim 1 , further comprising a control unit for controlling the first and second mechanisms.  
     
     
         23 . The press of  claim 1 , further comprising a first sensor for use in controlling a speed of the first mechanism.  
     
     
         24 . The press of  claim 23 , further comprising a second sensor for use in controlling a speed of the second mechanism.  
     
     
         25 . The press of  claim 24 , further comprising a control unit for controlling the first and second mechanisms, the control unit receiving inputs from each of the first and second sensors.  
     
     
         26 . The press of  claim 1 , wherein each of the first and second mechanisms comprise a belt drive.  
     
     
         27 . A method of controlling a tension and/or a speed of at least two belts in a press that comprises a first press roll and a second press roll arranged to form at least one nip, a first belt running through the at least one nip, a second belt running through the at least one nip, a sandwich stretch formed by the first and second belts being arranged after the at least one nip, a first belt drive for driving the first belt, and a second belt drive for driving the second belt, the method comprising: 
 driving the first belt at a first speed; and  
 driving the second belt at a second speed,  
 wherein the first speed is substantially the same as the second speed at least in a region of the sandwich stretch.  
 
     
     
         28 . The method of  claim 27 , further comprising moving the first belt, the second belt and the web disposed therebetween through the at least one nip before the sandwich stretch.  
     
     
         29 . The method of  claim 27 , wherein each of the first and second belt drives are arranged after the at least one nip.  
     
     
         30 . The method of  claim 27 , wherein the web comprises one of a paper web, a cardboard web, a tissue web, and a fibrous material web.  
     
     
         31 . The method of  claim 27 , wherein the at least one nip comprises an extended nip.  
     
     
         32 . The method of  claim 27 , wherein the first press roll comprises a shoe press roll and wherein the second press roll comprises a cylindrical mating roll.  
     
     
         33 . The method of  claim 27 , further comprising controlling the first and second belt drives.  
     
     
         34 . The method of  claim 27 , further comprising driving the second belt at a third speed after the second belt passes the second mechanism.  
     
     
         35 . The method of  claim 34 , wherein the third speed is greater than the first and second speeds.  
     
     
         36 . The method of  claim 27 , further comprising separating the first belt from the web after the sandwich stretch and driving the second belt at a third speed after the second belt passes the second belt drive.  
     
     
         37 . The method of  claim 36 , wherein the third speed is greater than the second speed.  
     
     
         38 . The method of  claim 36 , wherein the third speed is as much as approximately 4% greater than the second speed.  
     
     
         39 . The method of  claim 37 , wherein the third speed is between approximately 0.1% and approximately 0.3% greater than the second speed.  
     
     
         40 . The method of  claim 27 , further comprising separating the first belt from the web after the sandwich stretch and driving at least one of the first and second belts after the sandwich stretch at a third speed which is greater than a speed of the first and second belts before they enter the at least one nip.  
     
     
         41 . The method of  claim 40 , wherein the third speed is greater than at least one of the first and second speeds.  
     
     
         42 . The method of  claim 41 , wherein the third speed is as much as approximately 4% greater.  
     
     
         43 . The method of  claim 41 , wherein the third speed is between approximately 0.1% and approximately 0.3% greater.  
     
     
         44 . The method of  claim 27 , further comprising subjecting the second belt to a tensile stress after the sandwich stretch.  
     
     
         45 . The method of  claim 44 , wherein the second belt supports the web during the subjecting.  
     
     
         46 . The method of  claim 27 , further comprising subjecting the second belt to a higher tensile stress after passing through the at least one nip than before passing through the at least one nip.  
     
     
         47 . The method of  claim 46 , wherein the higher tensile stress is as much as approximately 6 KN/m higher.  
     
     
         48 . The method of  claim 46 , wherein the higher tensile stress is between approximately 0.2 KN/m and approximately 1.2 KN/m higher.  
     
     
         49 . The method of  claim 27 , further comprising controlling each of the first and second belt drives.  
     
     
         50 . The method of  claim 27 , further comprising controlling at least one of a speed and a tension of at least one of the first and second belts.  
     
     
         51 . The method of  claim 27 , further comprising controlling at least one of a speed and a tension of the first and second belts by controlling the first and second belt drives.  
     
     
         52 . The method of  claim 27 , further comprising controlling at least one of a speed and a tension of the first and second belts by controlling the first and second belt drives, whereby the first and second belt drives are controlled in a manner which minimizes a strain on the web.  
     
     
         53 . The method of  claim 27 , further comprising transferring the web from the second belt to a pick-up element after the web passes the second belt drive.  
     
     
         54 . The method of  claim 53 , further comprising guiding away the first belt after the sandwich stretch.  
     
     
         55 . The method of  claim 54 , further comprising driving the second belt at a greater speed than the first belt after the second belt transfers the web to the pick-up element.  
     
     
         56 . A press for processing a web comprising: 
 a first press roll and a second press roll arranged to form at least one nip;    a first belt running through the at least one nip;    a second belt running through the at least one nip;    a sandwich stretch formed by the first and second belts being arranged after the at least one nip;    a driven guide roll for driving the first belt, the driven guide roll being arranged after the sandwich stretch;    a driven suctioned guide roll for driving the second belt, the driven suctioned guide roll being arranged after the sandwich stretch; and    a system for regulating and/or controlling a speed of each of the first belt and the second belt.