Method and device in a press section of a paper machine for detaching a web from a face of a press roll

Press section of a paper machine, comprising

• a plurality of press rolls over which is arranged to run, at least two of said rolls being arranged in a nip-defining relationship such that a press nip is formed, a first one of said press rolls having a smooth mantle face,
• a transfer press element defining a transfer zone extending substantially between a point at which a transfer surface engages the web carried on said smooth mantle face of said first roll and a point at which the web is seperated from said smooth mantle face of said press roll for transfer to said transfer surface such that the web is transferred in a closed draw from said smooth mantle face of said first roll onto said transfer surface,
• suction means for subjecting the web to a negative pressure in said transfer zone at least prior to detachment of the web from the smooth face of said smooth-faced roll, said suction means being arranged in conjunction with said transfer press element such that suction is applied and air is drawn from said transfer zone through said transfer press element, said suction means applying a first negative pressure in said transfer zone through said transfer press element,
• heating means other than said smooth-faced roll for heating the web and/or the mantle face of said smooth-faced roll at a location between said press nip and said transfer zone such that the temperature of the web and/or the mantle face in said transfer zone is greater than about 50.degree. C. and less than about 100.degree. C. causing water between the mantle face and the web and/or in the web to be heated and then vaporized in said transfer zone, the water vapor having a second pressure, and
• regulation means for regulating the magnitude of negative pressure applied by said suction means and the temperature to which said heating means beat the web and/or the smooth mantle face of said smooth-faced roll in relation to each other such that the absolute value of the second pressure is substantially equal to or greater than the absolute value of the first pressure.

In a device in a press section for aiding in the transfer of a web from a press roll having a smooth mantle face and to intensify and improve the dewatering of the web passing through at least one nip defined by said smooth-faced press roll and a press roll, the device including a transfer press element defining a transfer zone extending substantially between a point at which a transfer surface engages the web carried on said smooth mantle face of said press roll and a point at which the web is separated from said smooth mantle face of said press roll for transfer to said transfer surface such that the web is transferred in a closed draw from said smooth mantle face of said press roll onto said transfer surface, the device further including suction means for subjecting the web to a negative pressure in said transfer zone at least prior to detachment of the web from said smooth mantle face of said press roll, said suction means being arranged in conjunction with said transfer press element such that suction is applied and air is drawn from said transfer zone through said transfer press element, said suction means applying a first negative pressure in said transfer zone through said transfer press element, the improvement comprising

• heating means other than said smooth-faced roll for heating the web and/or the mantle face of said smooth-faced roll at a location between said press nip and said transfer zone to a temperature greater than about 50.degree. C. and less than about 100.degree. C. causing water between the mantle face and the web and/or in the web to be heated and then vaporized in said transfer zone, the water vapor having a second pressure, and
• regulation means for regulating the magnitude of suction applied through said transfer press element via said suction means and the temperature to which said heating means heat the entire circumference of the mantle face of said smooth-faced press roll in relation to each other such that the absolute value of the second pressure is substantially equal to or greater than the absolute value of the first pressure.