Pickup & Transfer Rolls
The suction pickup and transfer rolls use vacuum to transfer the paper from the forming section to the press section and guide the sheet from one felt to another in the press section.
The suction press uses mechanical action to extract the water from the paper sheet. In the press section, large granite or hard rubber covered rolls are placed in close contact to form a "nip". As the paper passes through the nips, the water is pressed out of the sheet into press felts that transport and cushion the sheet on its journey through the press section. Presses can have suction or non-suction rolls to aid in the water removal process.
Once the a pressing action occurs, the press fabric (or "felt") contains a mixture of: water and chemicals; paper stock; other contaminents. Since each felt is a continuous loop, the water and contaminants must be removed prior to the next pressing action. Uhle boxes are stationary suction boxes that span the width of the felt and extract the water and contaminants accumulated by the felt in the pressing process. Each felt can have up to two uhle boxes per felt. Preseparation is required on all uhle box applications to prevent process water carryover into the vacuum pump.