| 摘要 |
<p>A web of tissue is formed in a crescent former, followed by an air press for water removal in the pressing section, passing onto a Yankee dryer (32). A headbox (22) injects stock between upper and lower dryer fabrics (26, 28) brought together on a breast roll (24). The fabrics move over vacuum boxes (42), and the web is heated with steam and passed between an upper pressure box (50) and lower vacuum box (52) forming an air press (48) which dewaters the web. A sheet transfer pickup vacuum box (54) holds the sheet to the upper fabric as the lower fabric diverges from the upper fabric. A pressure roller (30) transfers the web onto a Yankee dryer. The fabrics are cleaned on vertical runs (82) before returning to the breast roll. A second upper fabric or transfer fabric operating at a lower speed than the first can be used to form a rush transfer between the forming fabrics and the Yankee dryer which increases web bulk and absorbency. Instead of a second fabric, a vacuum pressure roll may perform the rush transfer between the lower forming fabric and the Yankee dryer. The lower fabric may be divided into two fabrics, and the second fabric which passes through the air press, can be used to mold a texture into the web. The rush transfer and the molding fabric may be combined in one machine. A twin wire former may be used instead of crescent former in each of the above configurations.</p> |
