Note: Descriptions are shown in the official language in which they were submitted.
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~SCREEN DECK"
BACKGROUND TO THE INVENTION
THIS invention relates to a screen deck apparatus and to a method of
screening particulate material.
In the handling of particulate material including agglomerations of
individual particles it is often desirable to disagglomerate the particles
to facilitate later operations on the individual particles. One example
where this practice would be desirable is in particle sorting, where
desired particles may be shielded in agglomerations of other undesired
particles and where the efficiency of the subsequent sort is dependent to
a greater or lesser degree on the exposure of discrete particles.
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SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a screendeck apparatus comprising a screen deck that includes a series of
flexible, parallel rods, and means for flexing the rods in a direction
transverse to their length.
In the preferred version of the invention, the rod flexing means operates
to flex the rods individually in sequence. Typically, the flexing means
includes one OT more contact members for contacting the rods
individually in sequence in a manner to cause the rods to flex
transversely.
The apparatus may also include means for causing relative movement to
take place, in a direction transverse to the rod lengths, between the
screen deck and the contact member or members.
In the preferred embodiment, the flexing means comprises a belt, one
or more projecting formations on the belt and means for moving the belt
relative to the screen deck so that the projecting formation or formations
contact the individual rods of the screen deck in sequence and cause
them to flex transversely to their length. ln ehis embodiment, the screen
deck comprises a first stringer to which one end of each rod is connected
and a second stringer which is spaced from and parallel to the first
stringer and which is formed with holes through which opposite end
regions of the rs)d project loosely. In this situation, the projecting
formations on the belt act on the opposite end regions of the rods.
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According to a second aspect of the invention there is provided a
method of screening particulate material, the method comprising the
steps of depositing the material on the surface of a screen deck of an
apparatus as summarised above, and ~lexing the rods of the screen deck
in a direction transverse to their length so as to cause disagglomeration
of the agglomerations in the particulate material.
In one application, the apparatus and method of the invention are used
to screen diamondiferous gravels or kimberlite ore.
BRIEF DESCRlPrION OF THE DR~VVINGS
.
The invention will now be described in more detail, by way of example
only, with reference to the accompanying drawings in which:
. Figure 1 shows a plan view of a screen deck apparatus of the- invention; and
Figure 2 shows a side view of the apparatus seen in Figure 1.
DETAILED DESCRIPTION OF THE DRAWINGS
The illustrated screen deck apparatus 10 incorporates a screen deck 12
composed of a series of closely spaced parallel rods 14. The rods 14 are
made of an inherently resilient material, such as plastics or metal, the
exact choice of material being dependent on the nature of the material
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which is to be screened by the screen deck 12. The rods 14 are quite
slender and therefore have considerable flexibility in a direction
transverse to their lengths.
One end of each rod 14 is fixed to a transverse stringer 16. The opposite
ends of the rods 14 pass through oversize holes 15 in a further stringer
17, so that the extremities 19 of the rods project past the stringer 17 as
illustrated.
The screen deck apparatus 10 also includes a flexing device 18. In thisembodiment, the flexing device 18 includes an endless belt 20 passing
around a driven pulley æ and an idling pulley 24. The belt 20 has a
series of spaced projections, in the form of rubber knuckles 26,
projecting from its surface as illustrated. The belt is arranged to move
over the extremities 19 of the rods 14, in a direction transverse eo the
lengths of the rods.
In use of the apparatus 10, particulate material which is to be screened
is deposited onto the upper surface of the screen deck 12, possibly along
a chute fed by a hopper or the like. At the same time, the belt 20 is
driven to cause the rubber knuckles 26 to brush over the extremities 19
of the rods 14 of the screen deck. As the extremity of each rod 14 is
contacted forcibly by a rubber knuckle, it is caused to flex resiliently in
a direction transverse to its length, as exemplified by the rods 14A in the
Figures. It ~,vill be appreciated that this flexure is permitted by the loose
passage of the rods through the oversize holes 15 in the stringer 17.
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As the relevant knuckle 26 moves on and breaks contact with the rod
extremity, the rod springs back to its original shape, but it will vibrate
to some degree before settling in the original, unflexed state.
Small, discrete particles having a dimension less than the initial rod
spacing will of course be able to drop through the screen deck
immediately. Larger agglomerations of particles that are unable to pass
through the screen deck will reside on the upper surface thereof. The
vibrations set up in the individual rods by passage of the rubber knuckles
26 over the rod extremities will tend to break the agglomerations up into
individual, discrete particles which will, if small enough, then be able to
drop through the screen deck.
It is therefore anticipated that the screen deck apparatus described
above will be useful in screening particulate masses, either alone or in
combination with other screening or sizing equipment. At the same time,
it is believed that the apparatus will function efficiently to exclude
particle agglomerations from the screened material. Naturally, the initial
spacing of the rods 14 will be chosen in accordance with the desired
particle sizes that are to be achieved in a particular application. In one
application, a screen deck apparatus of the kind described above can be
used to screen and disagglomerate diamondiferous gravels recovered
from alluvial deposits, or kimberlite ore recovered from underground
mining operations and subsequently crushed. In each of these cases, the
intention will be to remove oversize material and also to disagglomerate
the diamond particles from the associated non-diamond material.
.
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It will readily be recognised that the individual flexing of the rods 14,
leading to vibrations thereof, is of major benefit when compared to a
conventional vibratory screen. In a vibratory screen, the entire screen is
vibrated. This may well fail to break up individual agglomerations of
particles, which may tend merely to be shaken back and forth on the
surface of the vibrating screen. With individually vibrating rods in
localised zones of the screen deck, as proposed above, it is believed that
the potential for disagglomeration will be enhanced.
.
