Classifying – separating – and assorting solids – Sifting – Elements
Reexamination Certificate
1999-02-09
2001-04-17
Nguyen, Tuan N. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
Elements
C209S273000, C210S498000, C029S896600
Reexamination Certificate
active
06216877
ABSTRACT:
This invention relates to a screen device for screening fiber material and to a method of manufacturing this screen device.
The screening of fiber material, such as fiber suspensions of cellulosic material has the object to separate coarse particles in the form of shives, fiber bundles or other impurities from the fiber material. The screening normally is carried out in screen devices comprising a screen cylinder, which is stationary or rotary. The screen cylinder is provided with holes or slots, through which the fibers, but not the impurities, can pass.
Screen cylinders of this kind normally are manufactured by drilling holes or milling slots in a metal sheet which then is formed to a cylinder. For obtaining an open area as large as possible, i.e. the portion of the screen cylinder surface, which is perforated, the holes or slots must be arranged in dense relationship while at the same time the strength of the cylinder must be maintained. This requires great precision work.
Especially at the manufacture of slotted cylinders, which in certain cases are more advantageous than cylinders with drilled holes, difficulties arise concerning the strength, because the material remaining between the slots will be thin. The slots, therefore, must be milled short and at a certain distance from each other, which implies a restriction of the open area.
One way of solving this problem is to form the cylinder of a great number of bars, which are kept in place by ring-shaped ledges. This is, however, a complicated and expensive way of manufacturing a screen cylinder. It is also difficult to achieve a uniform slot width across the entire cylinder.
This problem is solved according to the invention by forming the screen device of a number of screen panels, which together form a screen cylinder. The screen panels are manufactured individually by forming them in one piece, whereafter the screen apertures are formed in the panels. A plurality of panels are thereafter assembled to a screen cylinder. The characterizing features of the invention are apparent from the attached claims.
The forming of the panels can be carried out by casting, extrusion, compression moulding or the like of a material, which consists of a suitable metal alloy or ceramic material, for example aluminium oxide. The material should be wear-resisting and un-weldable. After their forming, the panels are provided in a suitable way with screen apertures in the form of holes or slots. This can be brought about for example, by water-, laser- or electron-cutting. For improving the surfaces of the screen apertures still more, they can be polished, for example by wet abrasive polishing.
REFERENCES:
patent: 4374729 (1983-02-01), Frykhult
patent: 4795560 (1989-01-01), Chupka et al.
patent: 4986900 (1991-01-01), Mason
patent: 5064537 (1991-11-01), Chupka et al.
patent: 0 287 267 A2 (1988-10-01), None
patent: 0 357 382 A2 (1990-03-01), None
Lerner David Littenberg Krumholz & Mentlik LLP
Nguyen Tuan N.
Valmet Fibertech Aktiebolag
LandOfFree
Screen panel and method of its manufacture does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Screen panel and method of its manufacture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Screen panel and method of its manufacture will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469621