The invention relates to a screen grating for size-dependent separation of bulk materials, comprising a plurality of grating bars spaced apart one alongside another, which form a screen surface and which have a smaller dimension in the width direction, which runs parallel to the screen surface and perpendicular to the longitudinal direction of the screen grating bars, than in the height direction, wherein the height direction is perpendicular to the screen surface and perpendicular to the longitudinal direction of the grating bars and wherein the cross-section of the grating bars perpendicular to the longitudinal axis tapers with increasing distance from the screen surface in a first portion of the grating bars adjoining the screen surface, so that the width of a gap between two grating bars increases in the height direction in this height range.
U.S. Pat. No. 4,268,384 A presents a screen having conical grating bars that is used for separating solid materials from suspensions. For this purpose, the grating bars are to be arranged perpendicular to the transport direction.
DE 10 2014 011 679 A1 presents a screen device, which can be constructed as a screen drum having profiled bars. In order to reduce the tendency to clog, it is provided that the radii of the rounded flanks at the top of the screen bar have a common center point, wherein the screen bars can be arranged perpendicular to the conveying direction or at an angle to the axis of the screen drum.
Freely vibrating screen machines on the other hand, which essentially include circular vibratory screens, linear motion screens and elliptically vibrating screens, are usually supported via spring elements—directly or indirectly—on a base. A screen box having one or more screen gratings is set into vibration by means of a drive unit.
A problem addressed by the present invention is that of providing a screen grating of the type described above that has a lesser tendency to clog.
In a screen grating as mentioned above, the problem addressed by the invention is solved in that the cross section of the grating bars perpendicular to the longitudinal axis tapers down with increasing distance from the screen surface in a first portion adjoining the screen surface so that, in this height region, the width of a gap between two grating bars increases in the height direction, wherein the grating bars are parallel to one another, more particularly in the conveyance direction of the bulk material.
This can be implemented by shaping the first portion conically, i.e. by planes angled relative to one another.
In a simple embodiment, the first portion is formed from two flat plates that are arranged at an acute angle relative to one another, wherein the cavity formed by the two plates is closed off by a flat plate that runs parallel to the screen surface.
A second portion of the grating bars can be formed straight so that the width of a gap between two grating bars in this height area remains the same in the height direction. The tendency to clogging is already reduced due to the conical formation of the first portion. The second portion can, in particular, be formed in one piece with one of the two plates from the first portion that are arranged at an acute angle relative to one another. The first portion can be equally high as the second portion.
A plurality of cross-plates running in the width direction can be provided, which divide the gaps between two grating bars into a plurality of chambers.
As a rule, the grating bars are arranged parallel to one another, more particularly in the conveyance direction of the bulk material.
The grating according to the invention is preferably used in freely vibrating screen machines, which are usually mounted—directly or indirectly—on a base via spring elements, wherein a screen box containing one or more screen gratings is set into motion by means of a drive unit. Accordingly, the screen grating according to the invention can be part of a freely vibrating screen machine. In other words, the present invention can be implemented by equipping a freely vibrating screen machine with one or more screen gratings according to the invention.
The invention will now be explained in detail with reference to an embodiment. The drawings are for the sake of example and are intended to present the inventive concept but not to limit it or definitively reproduce it. Therein:
1 Screen surface
2 Grating bar
3 Cross-plate
4 Contact portions
5 First plate
6 Second plate
7 Third plate
8 Cavity
9 First portion of grating bar 2
10 Second portion of grating bar 2
11 Screen box
12 Drive unit
x Length direction
y Width direction
z Height direction
Number | Date | Country | Kind |
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50069/2016 | May 2016 | AT | national |