In a paper machine, stock flows from the headbox onto the forming wire. The wire is supported by the breast roll and couch roll. Foils and vacuum suction boxes remove water below the wire. This is the wire section. The sheet then moves to the press section, dryer section, size press, calender, and reel.
The vacuum couch roll and vacuum pickup roll both use vacuum to handle the wet sheet. They also have to match the speed of the sections around them. Their working principles and drive links are below.
Vacuum couch roll
The vacuum couch roll sits at the end of the wire section. It is common in fourdrinier, twin-wire, and gap-former machines. It supports the forming wire and helps drive it. Inside the roll, a vacuum chamber pulls air through the wire and the wet sheet. Water is removed, and the sheet is held against the wire or felt as it leaves the forming zone. This improves dewatering and helps transfer the sheet to the press section.
Roll body material matters. A stainless steel roll body has higher stiffness and mechanical strength than a tin bronze body. Its tensile yield strength and impact toughness are more than double those of bronze. This helps raise dewatering efficiency. Stainless steel also has higher hardness and wear resistance. It holds shape under long-term high alternating loads. Its corrosion fatigue strength, corrosion cracking resistance, and wear resistance are 2 to 3 times those of copper alloys. Service life is extended by 2 to 3 times.
For vacuum couch roll bodies and pickup roll shells, Hansheng Automation can machine custom stainless steel roll bodies, bearing housings, and seal components from customer drawings, in single pieces or small batches.
Vacuum pickup roll
The vacuum pickup roll sits between the wire section and the press section. It transfers the wet sheet from the forming wire to the press felt. A vacuum zone inside the roll holds the sheet against the roll surface. This reduces sheet breaks and keeps transfer stable. The roll usually has a vacuum chamber, sealing strips, and a suction opening. The vacuum level is set to match sheet grade, basis weight, and machine speed. Too little vacuum causes poor pickup. Too much vacuum can mark the sheet or increase drive load.
Drive connection
The vacuum couch roll is often a driven roll in the wire section. In traditional machines, it may be driven by the wire section main drive through a gearbox, line shaft, bevel gearboxes, and couplings. In modern high-speed machines, it is often driven by an independent variable-frequency motor as part of a sectional drive system. Its surface speed must match wire speed within a small tolerance. Speed mismatch causes wire wear, sheet breaks, or poor formation.
The vacuum pickup roll is usually driven by the press section or by its own variable-frequency motor. It must match the press felt speed. It also has to work with the wire speed so the sheet transfers without wrinkling or stretching. A small speed difference is sometimes used to keep the sheet taut, but the control range is narrow. The drive system uses a speed chain and tension control to keep all sections coordinated.
The two rolls are not normally connected by one mechanical shaft. Their link is through the drive control system. In modern paper machines, each section has a drive point. The PLC or DCS controls each motor and trims speed in milliseconds. Vacuum level is adjusted with machine speed and sheet grade. This keeps the couch roll, pickup roll, wire, and press felt working together.
Summary
The vacuum couch roll supports the wire, helps drive the wire section, and removes water at the end of forming. The vacuum pickup roll transfers the wet sheet to the press felt. Both depend on vacuum and on tight speed synchronization. Their drive link is mechanical in older machines and electronic in modern sectional drives. In both cases, stable tension and matched speed are what keep the sheet intact.
Beyond the parts discussed above, our precision component customization is not limited to this topic. We machine yacht precision components, RC car precision components, filling machinery parts, tobacco packaging machinery parts, printing machinery parts, food machinery parts, and medical device components. Hansheng Automation works from customer drawings and delivers one-off or batch parts to the required material, tolerance, and surface finish. Our scope is precision components, not complete machines.
