The Application of Doctor Blade in Paper Machine Different Position

Application and Classification of Doctor Blades in Paper Machine

Doctor blade is a common mechanical device in paper machines, which can be divided into two types: one is the doctor blade used for cleaning rollers and other equipment (including forming section and press section rollers, dryer cylinders, calendering rollers, and winding rollers); Another type is functional doctor blade, such as coating blade, creping blade, etc. This article mainly discusses the cleaning blade. Cleaning blade remove contaminants and water from the roller or dryer surface by maintaining the blade in a fixed position and swinging back and forth under the same pressure, such as swinging on a smooth press roller to remove debris caused by paper breakage. When used for roller cleaning and in conjunction with a spray system, doctor blade is an effective tool for maintaining fabric cleanliness, as most of the machine surface contaminants transfer from the fabric to the rollers’ surface. Doctor blade are commonly used to remove these pollutants in order to prevent their accumulation and re contamination or damage to fabrics.

Forming Section Doctor Blade

In the paper machine forming section, the doctor blade is used for breast roll, couch roll, inner and outer wire guide roll. The doctor blade of the breast roll requires a baffle to ensure that the white water enters the white water tray directly from the doctor blade seat. For the inner wire guide roll, the nozzle of the white water tray must flow directly from the blade into the forming fabric. For the external guide rolls of the fourdrinier paper machine, no special water treatment device is required, and water flows directly into the white water tray of the forming section. For the double wire former and mix former, special design is required to use the entire white water tray to receive water and remove fibers from the rollers. When the inner and outer wire guide roll is automatic adjusting roll or tension roll, Special brackets are required during operation to ensure that the doctor blade and roller remain in a fixed relative position.

Press Section Doctor Blade

The main function of the doctor blade on the top press roll is to promptly remove the damaged paper caused by the breakage of the transfer paper on the press roll. When the paper suddenly breaks on the press roll, if the paper is not transferred from the roller in time, it will cause the fabric (press felt) to be burned out and unusable. The function of using doctor blade to clean paper sheets is also to achieve the cleaning function of the roller. Therefore, the design of the doctor blade seat must be very sturdy and should also include a walking platform or paper transport device to catch the cleaned paper sheets.

The doctor blade on the felt guide roller can provide the best free cleaning for the fabric, especially the blade on the guide roller that comes into contact with the felt paper sheet side has a more obvious effect. Because the shredded paper, fine fibers, and other small solids in the pollutants will transfer from the press felt to the smooth roller surface, the doctor blade will remove these pollutants to prevent them from accumulating too much and contaminating the press felt. The doctor blade usually also includes a debris tray at this position to prevent debris from falling onto the press roller.

Dryer Section Doctor Blade

The dryer doctor blade is installed at the outlet position of each dryer to maintain the cleanliness of the dryer and improve the heat transfer efficiency between the dryer surface and the paper.

Calender Doctor Blade

When installed at the bottom of the calender or on the bottom roller of the calender, the function of the doctor blade is to remove the paper sheets caused by paper breakage and directly enter the paper damage pit. Due to the function of removing paper pages, the doctor blade holder must use a sturdy and durable design. The doctor blade of the middle roller is prioritized for cleaning the pollutants on the roller.

Reel Cylinder Doctor Blade

The function of the doctor blade at this position is to remove the paper sheets from the reel cylinder in case of paper breakage. As it is necessary to remove the paper sheets, a durable blade device must be used.