Classifying – separating – and assorting solids – Sorting special items – and certain methods and apparatus for... – Separating means
Reexamination Certificate
1999-12-08
2001-07-10
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Sorting special items, and certain methods and apparatus for...
Separating means
C209S659000, C209S660000, C209S671000, C209S672000, C209S673000
Reexamination Certificate
active
06257414
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to a roller sifting or dispersing machine for the classification or dispersing of wood chips, fibers, or similar materials and to the utilization of an above-described roller sifting or dispersing machine.
BACKGROUND SECTION
The problems arising in sifting and classification, as well as a pertinent portion of the state of the art, are described in EP 0 328 067. This published patent protects rollers whose sheathing surface is provided with tapering projections separated by tapering indentations. Neighboring rollers are arranged such that the outer ends of the projections are always opposite each other and are separated by an axially parallel gap; this gap defines the thickness of the chips to be sifted.
The prior art machine is described in U.S. Pat. 2,566,267. Here the annular grooves with a flush base as well as the crosspieces with a flush sheathing surface are always oblique to the roller axis.
SUMMARY OF THE INVENTION
The objective of the invention is to improve the sifting/classification effectiveness of the prior art described machine.
The objective is achieved by the fact that the annular grooves as well as the annular crosspieces that separate them, are located perpendicular to the surface of the roller axis, and the outer sheathing surface of each annular crosspiece is provided with adjoining teeth in the circumference direction; the front tooth-side in the direction of rotation is steeper than the adjoining tooth back-side, whereby, in the axial view, the crosspiece and teeth of a roller form a gradient that is opposed to the adjacent roller but has the same gradient height.
The leading tooth sides of the circulating teeth create a pitching effect on the particles of the material to be sifted/dispersed, so that clogging of the roller set are avoided and an accelerated movement, especially of the coarse matter, towards the exit end is achieved. Active impulses are generated only on the leading tooth-side while the particles falling on the tooth-backs essentially slide off. By the continuous opposing movement of the teeth, clogging of these openings for the passage of chips is avoided. In addition, the separation effectiveness can be regulated by modification of the roller revolution speed. For this, several sequentially switched roller sets with variable drives may be provided.
It is also possible to influence the separation efficiency by choosing different radial tooth-heights. Thus, the crosspiece teeth of the last rollers may exhibit maximal tooth height.
Fundamentally, it is possible to shape the bottom of each annular groove as a flat surface. For certain applications, however, is has proven advantageous for the bottoms of each annular groove to be provided with contiguous teeth in the circumference direction whose contours correspond to the crosspiece teeth, whereby the teeth of the annular groove are offset by a fraction of a tooth-width and tooth-backs slightly overlap the crosspiece teeth in the radial direction.
To avoid jamming of particles of the sifting material in the grooves, it is useful that the teeth of the groove are offset by less than one half of the tooth width in the rotation direction.
The previously described pitching effect is especially effective when the leading tooth-side makes an angle of about 45 degrees with the radius of the tooth-base.
It is further advantageous if a top-view rectilinear gap is provided between two adjacent rollers, such gap having a size of about 0.2× the height of the tooth. This relationship results from the determination that the gap size depends on the load on the teeth, where the loading with large teeth is higher than with fine teeth.
An especially favorable production process of the rollers can be achieved when each roller consists of individual pre-fabricated rings drawn on a roller body, where the roller body may consist of solid rods or thick walled pipe. The rings may have the same width, e.g. 3 mm, whereby the rings forming the annular grooves have an outside diameter only about 2 mm smaller than the outer diameter of the rings forming the annular crosspiece. For the construction of larger openings for the passage of chips, two or more identical rings may be arranged next to each other.
In view of the above, the invention concerns a roller sifting or dispersing machine for the classification or dispersing of wood chips, fibers, or similar materials, having at least one roller set that consists of several rollers arranged axially in parallel next to each other and having the same rotation direction; these rollers form a roller bed that extends in a longitudinal direction transverse to the rollers and has a feeding end for the material to be sifted/dispersed, as well as an exit end for the coarse material. Each roller turns toward the exit end with its upper side defining the roller bed; the roller is equipped with numerous annular grooves evenly spaced in the axial direction and separated by annular crosspieces; these grooves and crosspieces form the outer sheathing of the roller and adjacent rollers are arranged such that the crosspieces of one roller are opposite the grooves of its neighbor, thus being largely closed along their circumference when viewed along the roller bed surface, but having openings for the passage of chips in the direction perpendicular to the roller bed surface.
Other features of the invention as well as their utilization possibilities are the subject of the dependent claims and will be further clarified by embodiment examples that will point out further advantages of the invention.
REFERENCES:
patent: 2966267 (1960-12-01), Dunbar
patent: 4871073 (1989-10-01), Berry et al.
patent: 0328067 (1994-07-01), None
Gawlitta Werner
Gerhardt Klaus
Beauchaine Mark J.
G. Siempelkamp GmbH & Co.
McGuireWoods LLP
Walsh Donald P.
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