Classifying – separating – and assorting solids – Sifting – Elements
Reexamination Certificate
2002-08-15
2004-09-14
Kim, John (Department: 1723)
Classifying, separating, and assorting solids
Sifting
Elements
C029S522100, C029S896620, C209S407000, C209S409000, C210S498000, C210S499000
Reexamination Certificate
active
06789681
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a screen for fiber suspensions, more specifically, to a screen of the type (so-called bar screen basket) that is the subject matter of WO 98/57723 of the company Hermann Finckh Maschinenfabrik GmbH & Co.
Such a cylindrical or possibly also conical screen of rotationally symmetrical shape in relation to a screen axis has several ring-shaped profiled bar supports (also referred to as supporting rings) arranged at spacings from one another in the direction of the screen axis and lying in planes extending perpendicularly to the screen axis, and these profiled bar supports are provided at their inner or outer circumference, mostly at the inner circumference, with a ring of cutouts arranged at spacings from one another in the circumferential direction and opening towards this circumference of the supports. Viewed in the direction of the screen axis, the cutouts of the ring-shaped profiled bar supports lie over one another so as to enable straight profiled bars to be inserted into these cutouts and held therein. These profiled bars extend transversely to the circumferential direction of the screen, are arranged at spacings from one another in the circumferential direction of the screen and form between them slot-shaped screen openings of identical width which are interrupted by the ring-shaped profiled bar supports. All the profiled bars usually have the same configuration (the spacings of the supporting ring cutouts from one another are then all of the same size) and have a cross section of elongate shape, with the longitudinal direction of the profiled bar cross section being at least approximately radially oriented in relation to the screen axis. However, profiled bars of different configuration may also be used and arranged at such spacings from one another that the slot-shaped screen openings nevertheless are all of the same width. With an end region of the profiled bar cross section each profiled bar is inserted into a respective cutout of each one of the profiled bar supports, and, viewed in the direction of the screen axis, the shape of these cutouts corresponds to the configuration of this cross section end region of the profiled bars and forms at a radial spacing from the open end of the cutout an undercut in which a projection of the profiled bar cross section engages so that the profiled bars are positively held in the cutouts of the profiled bar supports, both in a radial direction in relation to the screen axis and in the circumferential direction of the screen. In the manufacture of such a screen, the profiled bar supports provided with the cutouts may initially be present in the form of straight bars or rails which after insertion of the profiled bars into the cutouts are bent into closed supporting rings so as to thereby clamp the profiled bars in the supporting ring cutouts when the cutouts are located at that side of the profiled bar supports which later forms the inner circumference of the supporting rings. As described in WO 98/57723, the straight or ring-shaped profiled bar supports may, however, also undergo such plastic deformation on that side of the profiled bars facing away from the open ends of the cutouts that as a result of displacement of profiled bar support material in the direction towards the profiled bars, their projections are pressed against the undercuts formed by the cutouts, and the profiled bars are thereby fixed in the supporting rings-this measure can be taken in both initially ring-shaped profiled bar supports and initially straight profiled bar supports, and, in the latter case, before or after the profiled bar supports are bent into closed supporting rings.
In the manufacture of the known screens disclosed WO in 98/57723, a fundamental problem arises in connection with insertion of the profiled bars into the profiled bar supports, irrespective of whether the profiled bars are inserted into the cutouts of still straight profiled bar supports or into the cutouts of supporting rings: As the profiled bar support cutouts each form an undercut in which a projection of the profiled bar cross section engages, the profiled bars must either be pushed into the profiled bar support cutouts in the longitudinal direction of the profiled bars or snapped into these cutouts transversely to the longitudinal direction of the profiled bars. In the former case, the insertion of the relatively long and thin profiled bars involves considerable difficulties as the profiled bars are to be held with a snug fit in the profiled bar support cutouts, which results in a high slide resistance, and, in the latter case, when snapping the profiled bars into the profiled bar support cutouts, if not a plastic deformation, then at least a considerable elastic deformation occurs in the webs of the profiled bar supports located between the profiled bar support cutouts. Even if these webs of the profiled bar supports only undergo elastic deformation when snapping in the profiled bars and thereby widening the profiled bar support cutouts, upon inserting the last profiled bar into the profiled bar supports the webs of the profiled bar supports adjacent to this profiled bar are unable to deviate or deflect at least to any appreciable extent towards both sides, quite apart from the fact that the snapping of the other profiled bars into the profiled bar support cutouts requires considerable forces if the profiled bars are to be held in a clamped and snugly fitting manner in the profiled bar support cutouts in the finished screen. The problems described hereinabove conflict, above all, with automated assembly of the screens.
The object underlying the invention was to create a screen of the generic kind as described in WO 98/57723 or in any of the publications (EP-B-0 417 408 and EP-A-0 499 154) mentioned in this document, which is easier to assemble than these known screens (bar screen baskets) and which basically opens up the possibility of automated assembly of the profiled bars in or on the profiled bar supports.
SUMMARY OF THE INVENTION
This object is accomplished in accordance with the invention by a screen in accordance with claim
1
and by a manufacturing method in accordance with claim
20
.
The invention thus relates to a screen for fiber suspensions having a shape which is essentially rotationally symmetrical in relation to a screen axis, with a first and a second circumferential side, one of which forms an inlet side and the other an outlet side of the screen for the fiber suspension, with a series of straight profiled bars arranged at spacings from one another in the circumferential direction of the screen, extending transversely to the circumferential direction of the screen and forming slot-shaped screen openings of identical width between them, the cross sections of the profiled bars each having an elongate shape with a first end region facing away from the second circumferential side of the screen and a second end region facing away from the first circumferential side of the screen, and with several ring-shaped profiled bar supports arranged at spacings from one another in the direction of the screen axis and lying in planes extending perpendicularly to the screen axis, each of the profiled bar supports having in its first edge region facing away from the second circumferential side of the screen a series of cutouts opening towards the first circumferential side of the screen, the shape of the cutouts-viewed in the direction of the screen axis-corresponding to the configuration of the second cross-sectional end regions of the profiled bars lying in these cutouts, and forming at a radial spacing from the first edge of the profiled bar support facing the first circumferential side of the screen an undercut in which a projection of the profiled bar cross section engages so that the profiled bars are held positively in a radial direction in relation to the screen axis and in circumferential direction of the screen with their second cross-sectional end regions in the profiled bar support cutouts, with the profiled bars
Czerwoniak Erich
Hutzler Wilhelm Hagen
Mayer Erwin
Pfeffer Jochen Gustav
Kim John
Leydig , Voit & Mayer, Ltd.
Voith Paper Patent GmbH
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