The function and structure of the upper breast roll on the Fourdrinier paper machine

The function of the breast roller on the Fourdrinier paper machine:

The breast roll is the first roll on the paper machine and is the beginning of the screen. One of its functions is to support the forming wire. The forming wire changes direction on the breast roll. After passing the breast roll, the non-working surface of the forming wire becomes the working surface. In many cases, the breast roll is also a dewatering element on the screen, and the pulp on the Internet can remove part or most of the water on the breast roll.

The structure of the breast roll on the paper machine:

The breast roller has a tube roller structure.

The breast roller should have sufficient rigidity and minimum deflection to prevent the copper mesh from wrinkling. In order to reduce the load on the breast roller driven by the copper mesh, the weight of the breast roller should be light. Generally, the breast roll of small and medium-sized low-speed paper machines is not medium-high, and the breast roll of large-scale high-speed paper machines is slightly medium-high.

In the past, breast rollers were mostly made of copper. Nowadays, thin-walled steel tubes are generally used, wrapped with 3-4mm thick copper skin or 8mm thick rubber (Brinell hardness 12-17 degrees). There are also breast rollers covered with FRP. The breast roller must be tested for static balance and dynamic balance.

In order to prevent the fiber from entering between the breast roller and the copper mesh, the roller surface is equipped with a plastic or wooden scraper to clean the roller surface, and a water spray tube is also installed between the breast roller and the lower lip to clean the roller surface. Usually, an extension plate is provided on the back of the scraper, and the white water removed by the net is introduced into the first white water tray.

The breast roll also has a dehydration effect, and the amount of dehydration can be controlled by the dots of the pulp flow. If the pulp flow directly falls on the breast roll, a large amount of water can be removed, which has a partial shaping effect. If the pulp stream is sprayed on the forming plate, the dehydration effect on the breast roll is very small, and the forming of the paper sheet is controlled by the table roll or the dehydration plate.

Modern high-speed paper machine that use free pulp to produce tissue paper use water-absorbing breast rolls for intense dehydration. In this case, most of the water is removed by the breast roller. The dehydration mechanism of breast roller is similar to that of table roller.