(57) A self-cleaning grid arrangement (11, 19) is provided for use in bulk materials handling,
e.g. quarry, chemical, waste or recycling industries during the conveyance of particulate
material to prevent the passage of oversize particles or foreign objects to the destination
of the particulate material. The grid arrangement (11) is formed of a first set bars
(12) disposed substantially parallel with each other, the bars (12) extending between
and being supported in holes (14, 21) in the sides (13, 22) of a chute (10) in which
the bars (12) are free to rotate and/or reciprocate lengthways. At least some of the
bars (12) have disturber plates (31) extending upwardly therefrom spaced along their
length. As a result of such rotation and/or reciprocation, if particulate material
does stick to or coagulate above a bar (12), there will be a lesser tendency for any
material to bridge to an adjacent bar (12) and an increased tendency for the particulate
material to fall between the bars (12). The bars (12) are curved along their length
and have a radius of curvature greater than the length of the bars (12) between the
sides (13). Each bar (12) has one end (16) depending from the remainder of the bar
(12) in the direction away from the centre of curvature of the bar (12). A second
set (19) of bars (20) that are substantially parallel with each other, is disposed
substantially at right angles to the first set of bars (12). The bars (12, 20) may
be inclined, and bars (26) may be tapered towards their lower ends. The support structure
for the bars (12, 20) has inner (13) and outer (32) side plates so that particulate
material passing through the holes (14) in the inner side plates (13) pass through
a passageway (33) between the side plates (13) and outer side plates (32) and are
returned to the lower part 28 of the chute (10).
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