Abstract: A screen cylinder, screen, method of manufacture of the screen cylinder, and method of use of the screen cylinder, allow screen capacity to be maximized without sacrificing screen cylinder strength, and while achieving a clean accepts flow. A screen cylinder is constructed in a conventional manner except that at least one reinforcing ring is permanently fastened (typically by continuous or spot laser or electric beam welding, or direct resistance welding) to at least a majority of (and typically essentially all of) the land areas which separate grooves in a row from each other, at the outlet surface of the cylinder, or at least one spiral ring is applied. In this way effective slot length of screen cylinders may be about 65-90% of the total screen length, compared to only about 45-55% for conventional screen cylinders. The screen cylinders are particularly effective in screening cellulose pulps from the pulp and paper industry.

Abstract: A method is disclosed for the manufacture of screen cylinders, e.g. for removal of debris such as sand, rock, metal, resin etc. from a liquid suspension used in the pulp and paper industry. The screen is of the type having a plurality of slot passages, each extending axially the entire axial length of the cylinder. According to the invention, the width of the slots is controlled by determining the physical structure of the screen, particularly the overall thickness of the screen and the backing reinforcement ribs, prior to the rolling of the screen plate into a cylinder. A table of a number of different sizes is included showing the practical range of application of the invention. The invention allows the use of standard cutters used in the milling of the slots for the production of screens with much narrower slots to obtain an improved degree of removal of contaminants without having to use specially thin cutters. Screens produced by the method are also claimed.

Abstract: The differences in performance of a screening cylinder during screening of a fiber suspension (e.g. low consistency paper pulp) at the inlet end compared to the reject end is accommodated by constructing the feed side surface of the screening cylinder so that it induces greater turbulence in the vicinity of the screen cylinder surface adjacent the reject end of the screen than adjacent the inlet end. Typically this increase in turbulence is at least about 10% (preferably at least about 40%, and typically greater than 100%). The turbulence increase can be provided by a substantially smooth screening medium surface at the inlet end and a contoured screening medium surface adjacent the reject end, or by first and second contoured surfaces of different aggressiveness.

Abstract: A screen cylinder or plate has a screening surface and accepts surface on opposite faces, and screens pulp flowing in a flow direction to separate accepts from rejects. A number of substantially parallel macro grooves are formed in the screening surface generally transverse to the flow direction, and a number of parallel micro grooves are formed in the screening surface within each macro groove also generally transverse to the flow direction. The macro grooves induce shear stress in the reject material flowing in the flow direction to keep it in constant motion and to prevent it from forming a mat on the screening surface. The micro grooves induce micro turbulence into the pulp at the immediate area of screening openings extending from each micro groove to the accepts surface, to fluidize the pulp so that accepts readily pass through the screening openings toward the accepts surface. Each micro groove within a macro groove is located further away from the accepts surface moving in the flow direction.