Novel approach to optimizing sheet formation on the fourdrinier. Part 1: Vibrating the forming fabric vertically at or near its resonant frequency

Recognizing the limitations of conventional dewatering devices, we began about ten years ago to seek alternative approaches of generating microturbulence during the dewatering of stocks on the fourdrinier, especially at higher machine speeds. We began with an examination of the nondewatering means known at that time for generating such energy. They were all found to have certain drawbacks. It now appears that all of these problems can be virtually overcome by two relatively new devices employed in tandem on the fourdrinier. One is a large-capacity dewatering element that does not generate any turbulence whatsoever, the Wunderfoil. The second is a roll mounted under the fabric, the Sheraton Roll, which imparts fine-scale, vertical mechanical pulses (that is, a vertical shake) into the stock while causing only minimal dewatering. In one recent installation of a modified Sheraton Roll, this roll was discovered to have considerably greater potential than originally anticipated. In this article, we will take a close look at the theory and operation of this modified Sheraton Roll. This involves vibrating the forming fabric vertically at or near its resonant frequency.