Note: Descriptions are shown in the official language in which they were submitted.
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This invention relatsg to apparatus for conveying particulate
materi~l ahd ~as particular but ~ot ~xclu~i~e reference to
conveyors for use ln conveyin~ do~estic re~u~e~
So~e materials are relatively ea~lly co~vey~d when in part-
iculate ~orm. I~ the ~aterial i8 dr~ it b~have~ al~o~t a~ a
fluid a~d is ~imply handled and ~imply meteFed. O~her materials
are more dif~icuIt to convey~ particularly i~ a controlled rate
o~ supply is rsquired at some ~ta~e. ~ partiGularly dif~icult
material to ha~dle i~ domestic refu~e. By it nature, domestic
refuse is not a unirorm material a~d apart f~om problem~
associatsd w~th moi~ture cont~nt tend~ to cQmpaot ~ ~laced in
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pile~ havin~ thic~nesse.-s of 2 metre~ or more. I~ de3ired
to convey do~estic refu~e, for example~ to an ~ncinerator ~o a
boiler in wh$ch the rs~use i8 used as a ~uel suppleme~t~ there
are occa~ion~ when a controlled feed rate o~ refuse is requirsd.
It ha~ proved extremely di~ficult to obtain ~uch a c~ntrolled
delivery rate wit~ untreated domestic re~use. Th~ main method
of obtaining controlled rate~ of refu~e ~lo~ ha~e utili et the
so~called "Atlas Tank3". The~e are conical ~ank~ having ~heir
apex pointing upwardly and haYing a capaoity of up to 500 tonsO
The tanks can be 100ft high. Refuss i~ ~oured in through the
top of the tank and is extracted ~rom the bottom by ~ean~ of a
chain of buckets which i~ pulled round the bottom o~ the tank
and feeds the r~fuse into a trou~h fro~ wh ch it i5 remo~ed by
mean3 of a ~-onventional endle~ belt conveyor~ Unfortunately~
hweVer~ the chaln o~ bucket3, which i~ ~ree at one end~ tonds
to leave an undi~turbed conical pile in the middle o~ the ta~k
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and this pile can fcrment and even in certain circumstances catch fire. Also
the bucket chain tends to wear out the botkom of the tank meaning that the
floor must be replaced at fairly regular intervals which can be as short as
one year.
If a so-called "live-bottom tank" is used then there is a tendency
for tlle refuse to compact onto the conveyor and very thick layers of refuse
will at times be delivered. Thus if the conveyor belt operates at the bottom
of a pile of refuse and is fed with very thick layers, for example 2-3 metres
or more, then a very thick layer will be delivered by the belt. Attempts
were made by the inventors to control the thickness of the layer by using a
weir or wall across the top of the belt to restrict the passage o~ the refuse.
If was found, however, that this resulted in jamming because the domestic
refuse bridged the gap between the weir and the belt forming a solid block
which prevented the conveyor belt from opera~ing.
The present invention provides a method of conveyin~ particulate
matter for delivery at a controlled ra~e co~prising feeding said matter onto
a moving upwardly inclined surface and during conveyance by the said surface
subjecting said matter to the actionl~o-f a plurality of driven screw conveyors
arranged side by side in spaced substantially parallel relationship, each
screw conveyor having its axis of rotation in a vertical plane which extends
longitudinally of ~he inclined surface and converging towards the discharge
end of the~upwardly inclined surface, and adjusting the direction and speed
of the screw conveyors to control the delivery of matter at the upper end of
the moving upwardly inclined surface.
The present invention also provides apparatus for conveying particu- ;
late material, the apparatus comprising an inclined conveyor operable to
convey said material in an upward direc~ion and, located above the upper end -
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region of the inclined conveyor, a rotatable drivable screw conveyor orienked
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with its axis of rotation lying substantially in a vertical plane tha* extends
longitudinally of the inclined conveyor and said axis and the line of movement -
of the inclined conveyor converging towards the discharge end of the conveyor
so as to co-operate with the inclined conveyor in controlling, in use, the
amount of material that is delivered at the upper end of the inclined conveyor.
There is preferably a space between the bottom of the screw conveyor(s) and
the conveyor belt. The space may be fixed or may be adjustable.
The axis of rotation of the or each screw conveyor is advantageously
substantially horizontal.
The belt is preferably an endless belt.
Preferably there is at least one pair of screw conveyors operating,
in use, to screw material in a direction substantially opposite to the hori
zontal component of the conveyor belt i.e. in a reverse direction. There may
be a plurality of pairs of screw conveyors operating in the reyerse direction.
The or each pair of screw conveyors preferably comprises a first conveyor
- having a right-handed thread and a second conveyor having a left-handed thread,
the direction of rotation of the first conveyor being opposite to the direc-
tion of rotation of the second conveyor~
Alternatively one or more screw conveyors may operate in a forward
direction ~i.e. in the same general direction as the movement of the belt~ and
preferably in such a circumstance each such screw conveyor has a material-
moving capacity in excess of the moving capacity of the belt. The material
to be conveyed is preferably fed onto the conveyor or in the form of discrete,
preformed blocks, the length of the screw conveyor(s) preferably being equal
to or greater than the length of each block of particulate material i.e. the
` dimension of each block in the direction o movement of the belt presented to
; the screw conveyor(s) by the belt.
The belt conveyor may be located so as to form at least part of the
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base of a container into which the particulate material is loaded. The belt
conveyor may have transversely extending slats across at least part of its
surface.
In a preferred embodiment there is a plurality of screw conveyors
which are preferably uniformly spaced over substantially the whole width of
the belt conveyor, the screw conveyors operate in the forward direction. The
right-hand side
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conveyor(s), viewed ir, the direction of movement of
the belt, may have right-handed screws and the left-hand
side screw conveyor(s) may have a left-handed screw. In an
alternative form, the conveyors ~ay have right- and left-
handed screws alterna~ely-across the width of the belt.
There may be one or more central screw conveyor(s) in the
arrangement in which there is a plurality of screw conveyors
adapted to operate, in use, in the forward direction of the
movement of the conveyor belt, the central screw conveyor(s)
operating in the reverse direction. In-such an arrangement,
a single central screw conveyor will act to split the output
material of the conveyor into two separate portions. If three
or more portions are required then two or more conveyors
operating in the reverse direction may be used.
The screw conveyors may all be operated by a single motor
drivably connected to the conveyors by suitable ~ear means to
maintain a fixed rate of operation of the conveyors.
For dry refuse, screw conveyors operating in the forward
or backward direction may be used. For wet refuse, however,
reverse acting screw conveyors are preferred.
By way o~ example embodiments of the present inventior- will
now be described with reference to the accompanying drawings of
which:-
Figure 1 is a schematic cross-section of a conveyor system
not in accordance with the invention;
Fiæure 2 is a schematic cross-section of a live-botto~
pit conveyor constructed in accordance with the
invention.
Figure 3 is a partial schematic view along the line of the
arrow III of Figure 2; and
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~igure 4 is a partial schematic view similar to that
of FigurP 3.
Re~erring to Figure 1 this shows a live-bottom pit generally
indicated by 1 having a fixed side wall 2 and an endless belt
conveyor 3 which forms the base/side of the pit. Domestic refuse
may be tipped into the pit as shown by the arrows 4. When
the conveyor 3 is operated the surface 5 moves in the direction
Or arrow 6 and carries with it a very thick layer of domestic
10 refuse 7.
In order that the domestic refuse could be delivered at a
controlled rate a weir or wall 8 was placed across the top of the
conveyor. Initially a controlled layer 9 of domestic refuse
passed underneath the wall 8 and fell off the end of the con-
15 VeyOr. It was found, however, that the small gap 9 rapidly
became bridged by the domestic refuse which piled up against the
wall 8 jamming the conveyor and preventing further operation of
the system. Solutions to this problem have been found by
utilisin~ the conveyor-as shown in Figures 2, 3 and 4.
Again domestic refuse 4 is tipped into the live pit which
has side walls 2 and a live base constituted by endless conveyor
belt. Five screw conveyors 10 are located above the upper end
region of the belt 3. Four of the screw conveyors 10 operate
in the forward direction of travel as illustrated by the arrow
11, the fifth, central conveyor, operating in the reverse direction
(see Fig. 3). The length L of the conve~ors 10 is grsater than
or equal to the length of preformed blocks o~ domestic refuse
presented to the conveyors by the endless belt 3 and, as can be
seen, the right-hand end of each conveyor 10 lies directly above
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the upper end of belt 3.
Referring now to Figure 3, the outer two conveyors 12 and 13
are rotated in a counter-clockwi~e direction when viewed in th~
direction III indicated in Fig.2. The conveyors 12 and 13 each
have a right-hand screw and tend to push the material kowards
the centre of the conveyor belt 3. The outer two conveyors
14 and 15 each have a le~t-hand screw and are rotated in a
clockwise direction when viewed along the arrow III. Conveyors
14 and 15, therefore, also screw the material towards the
centre of the conveyor belt 3. The central conveyor 16 alf~o has
left-hand thread but is rotated in a counter-clockwise direction
so as to screw material backwards against the direction of travel
of the belt 3. This results in the refuse falling off the
upper end of belt 3 in distinct portions 17 and 1~.
It will be appreciated that the conveyors 12 to 16 could be
alternatively right and left-handed rather than being paired as
shown in Figure 3.
; In operation the screw conveyors 10 are operated at a
faster delivery rate ~hat the belt conveyor 3. The belt conveyor
3 can therefore, ba regarded as presenting material to the screw
conveyors for ~urther movement o~ the material. Since the screw
conveyors 10 are operating at a ~aster rate than the rate o~
delivery of the belt 3 they do not become jammed or clogged and
this means that a ~ree-running conveyor system is provided.
It will be appreciated, however, that the rate o~` delivery of
material overall is dictated by the rate of movement o~ the belt
3. This is because the belt 3 delivers material to the conveyors
10 which is subsequently moved away by the conveyors. Clearly,
however, screw conveyors can only move material presented
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to them and varying thc rate of feed supplied by the belt 3
will alter the rate of feed of the conveyors 10.
Although such an arrangment including forward operating screw
conveyors 10 works satisfactorily on dry refuse it has been found
that with refuse containing large quantities of water ~during the
winter months the water content can increase to 50% by weight of
the total refuse handled) the refuse tends to jam and is not
properly metered but is passed out in large lumps.
A solution to this is to run all of the screw conveyors
in the reverse direction. In particular if the conveyors
are arranged as shown in Figure 4, in pairs, particular
advantages can be obtained. By running the conveyors 17 and 18
in the opposite directions - the conveyors 17 and 18 themselves are
opposite handed - the refuse is churned up and aerated. This
breaks down the compacted refuse-into a light aerated stat~
which means it is more easily handled. The conveyors may be
operated as shown in Figure 4 at 19 and 20 in which case the
aeration action would take place on the outside of each pair
rather than at the centre.
Preferably the gap 21 between the belt conveyor and the
screw conveyors is adjustable to take account o~ the vari~tion
in density of the material being handled. Tbe gap should be
larger for low density material such as waste paper and smaller
for higher density material such as waste sawdust. Once set
the gap can be 'eft durin~ normal running~ Because the screw
conveyors are operating in the reverse direction to the belt
conveyor there is a considerable amount of shear taking place
in the refuse between the conveyors. This means that adequate
torque must be available to drive the belt and the screw
conveyors.
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Although the invention is particularly adapted for conveyin~
~omestic refuse any other suitable particulate material may be
conveyed by the conveyors of the invention. Thus, for example,
material such as damp sand or other difficult to-handle material
could easily be dealt with by the invention.
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