paper mill bearings
The Paper Machine.
The refined material is blended with specific auxiliary substances (depending on the peculiarities the material must have) and it finally reaches an inflow tank in which the suspension is evenly spread on a former canvas
The continuous stroke between filtering and re-flocculation generates the sheet.
The best known system all over the world is the plane table machine even if, nowadays, remarkable technological innovations such as the ‘Twinformer’ and the ‘Gapformer’ are available.
The first system consists of an upper canvas and various draining tanks so that the fibrous suspension can be drained off upward and downward at the same time. The positive effects are the reduction in the drainage time, the increase of the production speed and a greater uniformity on both surfaces of the paper sheet.
The second system consists in the injection of the suspension directly from the draining tank between two canvases and the simultaneous draining off from both sides so that the mixture is stuck, almost ‘frozen’, for few milliseconds while leaving the draining tank.
After that, the structure of the paper cannot be influenced by the drainage elements any more.
This process requires considerable efforts in the accuracy and the quality of the draining tank and of the costant part.
Once generated, the sheet is subjected to a further drainage phase by means of a mechanical pressure carried out by a series of cylinders. In recent years the cylinders have been replaced by sliding blocks that make the compression more efficient.
The remaining water after the drainage is removed through evaporation.
The drying is generally achieved by contact. The sheet of paper is passed through a series of drainage cylinders.
After drying the paper is smoothed by means of calenders.
Scraping rollers are used to keep the cylinders clean and, therefore, riduce the possibility of sheet rips.
This type of bearings can be, also, employed in the following processes:
- Superficial treatments
- Coating
- finishing
