Note: Descriptions are shown in the official language in which they were submitted.
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COMPACTION METHODS AN APPARATUS
RELATED APPLICATIONS
This application is filed as a division of Canadian patent application serial
No. 2,264,817,
and which was filed as the Canadian national phase entry of International
application No.
PCT/GB97/02387 filed OS September 1997.
SCOPE OF THE INVENTION
The present invention relates to compaction methods and compaction apparatus
and in
particular but not exclusively to methods and apparatus for compacting (i.e.
compressing) waste
material. Other applications for the invention include the compaction of waste
materials used in
farming and the food industry, but not necessarily waste materials.
Compacting apparatus is described in International Patent Application No. WO
94/07688. That apparatus uses a hopper to supply material to a screw conveyor
which conveys
material through a passage to cause compaction. The compacted material then
leaves through an
exit nozzle. A control circuit is provided to sense when the compacting
apparatus becomes
blocked. When this happens, the screw conveyor is reversed to draw compacted
material back to
the hopper, with a view to clearing the blockage. It has been found that even
if this technique for
clearing blockages is effective, its reliance on a potentially complex and
expensive control
arrangement can prevent its use for certain commercial applications,
particularly with relatively
small, cheap compacting apparatus. The present inventor has therefore sought
to provide
improved compacting apparatus.
The present invention provides compacting apparatus comprising a screw
conveyor for
axial rotation to convey material through a passage and compact it therein,
and an exit nozzle
communicating with the passage, the screw conveyor being supported for axial
movement
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relative to the passage during use, whereby the screw conveyor may move
axially in the event
of a blockage.
The screw conveyor is preferably resiliently biased in the axial direction
relative to the
passage. The screw conveyor may be biased to move relative to the passage in
the conveying
direction. At least part of the screw conveyor is preferably located within a
tapering part of the
passage and has a diameter which tapers in the same sense, whereby axial
movement of the
screw conveyor relative to the passage varies the gap between the tapering
part of the screw
and the tapering part of the passage. The tapering parts of the screw conveyor
and
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passage may have substantially the same degree of taper.
Preferably fixed blade means are located adjacent the screw conveyor,
and cooperating blade means are carried by the screw conveyor, whereby
material located between the said blade means is subjected to a cutting action
by continued rotation of the screw conveyer. The cooperating blade means may
be located along the outer edge of the flight of the screw conveyor. The
cooperating blade means may extend over a greater axial length of the screw
conveyor than the fixed blade means, whereby the blade means remain in
cooperation over a range of positions of the screw conveyor relative to the
passage. Preferably at least part of the cooperating blade means are located
along a tapering portion of the screw conveyor.
In a second aspect, the invention provides compacting apparatus
comprising a screw conveyor for conveying cvaste material through a passage
and compacting it therein, and an exit nozzle communicating with the passage,
the nozzle defining an internal transverse cross-sectional area which enlarges
and reduces respectively in response to increasing and decreasing material
pressure, and wherein the nozzle comprises at least one resilient member
which causes the nozzle to be biased toward a position of minimum cross-
sectional area, the or at least one resilient member comprising an inflatabie
portion which provides an adjustable degree of resilience dependent upon the
degree of inflation of the resilient portion.
Preferably the nozzle has a plurality of wall portions which are movable
relative to each other to vary the cross-sectional area of the nozzle, the
resilient
member cooperating with the wall portions to bias the nozzle toward a position
of minimum cross-sectional area.
The nozzle may comprise a number of spaced apart, longitudinally
extending fingers. Preferably there are no gaps between the fingers and the
nozzle tapers towards its outlet when the nozzle cross-sectional area is at
its
minimum. The nozzle may comprise two members each of which has a
CA 02450046 2003-12-18
number of spaced apart, longitudinally extending fingers, one member being
arranged
inside the other. The resilient member may be located to surround the outer of
the two
members to provide resilient bias thereto. Preferably the two members are
arranged such
that a finger of one member overlaps two fingers of the other member whereby
there are
substantially no gaps between the fingers.
In another aspect, the invention provides material handling apparatus
comprising
compacting means operable to compact material and to deliver compacted
material to
collection means, the collection means providing a plurality of locations at
which
compacted material may be received, and being movable to allow one location to
move to
an emptying position while another is moving to a position for receiving
material from the
compacting means.
The collection means may comprise a rotatable carousel. Each location may be
adapted to removably receive a receptacle which can be removed when full for
replacement by an empty receptacle. The receptacle may be a bag or bin liner.
Preferably the apparatus comprises means operable to detect the weight of
material
received at a location and to cause the collection means to move when the
received weight
exceeds a threshold value.
Preferably the compacting means comprises a screw conveyor which has a
substantially vertical orientation to drive compacted material up to a
position from which
the material may fall to the collection means.
Accordingly, in another aspect the present invention resides in a compacting
apparatus comprising a screw conveyor for axial rotation to convey material,
in use,
through a passage and compact it therein, and an exit nozzle communicating
with the
passage, the screw conveyor being supported for axial movement relative to the
passage
during use, whereby the screw conveyor may move axially in the event of a
blockage, and
there being fixed blade means located adjacent the screw conveyor, and
cooperating blade
mans carried by the screw conveyor, the fixed blade means and the cooperating
blade
means causing material located between the said blade means to be subjected to
a cutting
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3a
action by continued rotation of the screw conveyor, and the cooperating blade
means
extending over a greater axial length of the screw conveyor than the fixed
blade means,
whereby the blade means remain in cooperation over a range of positions of the
screw
conveyor relative to the passage.
Embodiments of the present invention will now be described in more detail, by
way
of example only, and with reference to the accompanying drawings, in which:
Fig. 1 shows a longitudinal cross-sectional view of a compactor;
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Fig. la shows an enlarged view of part of the compactor of Fig. 1;
Fig. 2 shows a longitudinal cross-sectional view of the compactor of Fig. 1
when filled with waste material;
Fig. 3 shows a cross-section of the compactor of Fig. 1 along line III-III;
Fig. 4 shows a perspective view of the nozzle of Fig. 1 which has been
partially cut away for clarity;
Fig. S shows a cross-sectional view of the output end of the compactor of
Fig. 1, with the screw conveyor packaged for transportation;
Fig. 6 shows a cross-section view of the output end of the compactor of
fig. I, when filled with waste material;
Fig. 7 shows a cross-sectional view of the screw conveyor of the
compactor of Fig. 1; and
Fig. 8 is a highly schematic perspective view indicating one application of
apparatus according to the present invention.
As can be seen from Figs. 1 to 7, the waste compaction apparatus 2 has a
screw conveyor 4 which conveys as well as compacts material along a passage 6
from an inlet 8 to an exft nozzle 10.
The passage 6 is generally cylindrical and has a first part 12 of generally
uniform cross-section. The first pan 12 of the passage has a longitudinally ex-
tending opening 14 through which uncompacted waste material is fed from the
hopper 16. The sue of the hopper 16 is selected so as to prevent over-filling
of
the apparatus. In practice, this first part 12 is in the form of a trough
having a
rounded bottom 18 (see Fig. 3), the sfdes of which also define the hopper 16.
The trough opening defines the longitudinally extending opening 14.
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The passage 6 also has a second part 20 which is tapered in the direction
towards the exit nozzle. This second part 20 thus has a generally frusto-
conical
shape.
The inner walls of the passage 6, both in the first part 12 and the second
part 20 are provided with longitudinally extending ribs 22 which project
inwardly into the passage. These ribs 22 prevent partially compacted material
from rotating with the screw conveyor 4.
The inner walls of the first part 12 of the passage are provided with two
projections 230 (see Fig. 3> which extend along its Length. These two
projections 230 are arranged to contact the outer periphery of the screw
conveyor to cut up elongate waste material such as plastics bin liners and the
.,
like. This prevents such material from wrapping itself around the screw
conveyor and causing it to Jam. The projections 230 are provided with a
cutting
edge for this purpose. The outer periphery of the screw conveyor may also be
provided with a sharpened edge to cut up the material. Where appropriate the
ribs 22 are also able to provide a cutting surface or anvil against which the
flight 24 of the screw conveyor 4 can act to break the waste material down
into
smaller pieces which are more easily compacted.
The screw conveyor 4, which is illustrated in detail in Fig. 7 has a first
part 26 where the flight is of uniform diameter. The length of this first part
26
corresponds substantially to the length of the first part 12 of the passage 6.
The flight diameter of the second part 28 of the conveyor =i decreases in a
manner which corresponds generally to the degree of taper of part 20 of the
passage 6. The diameter of the flight 24 of the screw conveyor is selected
such
that there is usually a fetv millimeters clearance between the screw conveyor
4
and the projecting ribs 22. Typically this clearance is in the range of 2 to
3mm.
The screw conveyor 4 has a third part 30 in the form of a shank with no
flight which extends tnto the nozzle 10. When the apparatus 2 is in use, the
annulus of moving compacted waste material 65 in the compaction chamber
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6
200 of the nozzle 10 acts as a bearing and supports the third part 30 i.e. the
threadless axial shank of the screw conveyor 4. It has been found that the
screw conveyor 4 is centred as well as supported by the waste material in the
compaction chamber 200 so that the flight 24 no Longer contacts the bottom 63
of the passage 6.
The pitch of the screw conveyor 4 also varies along Its length. In
particular the pitch of flight 24 decreases in the direction towards the
second
tapered part 28. The decrease in pitch of the screw conveyor 4 as well as the
tapering of passage 6 enhances the degree of compacrion achieved by the waste
compaction apparatus 2. The pitch of the screw conveyor is of course selected
depending on the material usually to be compacted as well as the degree of
compaction required.
The thickness of the flight 24 changes along the length of the screw
conveyor .~ and, in particular increases as the pitch decreases. Thus, the
part of
the flight which is subjected to the greatest force as a result of the
tapering
passage and reduced pitch, has the greatest thickness to withstand that
increased force and the resulting increase in wear. The life of the screw
conveyor ~l is thus increased. Likewise, those parts of the conveyor which are
subjected to least force have the smallest flight thickness. This results in a
useful reduction in the weight of screw conveyor especially since the part 34
of
the flight 24 having the least thickness has the largest diameter. In
practice,
the thickness preferably begins to increase slightly upstream of the tapering
part 28, although this is not appreciable from the drawings. The dimensions
for pitch, flight thickness and flight diameter can all be varied in
accordance
with the application and size of the apparatus.
The screw conveyor 4 is made from any suitable material which has the
desired strength, rigidity and resistance to wear for the particular
application in
question. For example the screw conveyor 4 may be of mild steel.
In accordance with the invention, the screw conveyor 4 is mounted to
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WO 98109801 PCT1GB97/02387
allow some degree of axial movement relative to the rest of the apparatus,
while
rotating. More specifically, the conveyor 4 is slidably mounted on a shaft
300,
either by splines 301 as shown or by the shaft 300 having a non-circular cross-
section, or similar. The shaft 300 extends out from the upstream end of the
conveyor 4, by means of an extension 60, to a gearbox/beartng 69 through
which the conveyor is driven by a drive motor 66. The shaft 300 therefore
drives the conveyor 4 to rotate, while being able to move axially.
The screw conveyor 4 has a collar 225 against which a resilient bias
means 302 acts. The bias means 302 is shown schematically as a compression
spring acting between the collar 225 and the housing of the bearing 69 but it
will be appreciated that many alternatives are possible, including compression
or extension springs, hydraulic or other pressure arrangements to push on the
screw conveyor 4, and others. Alternatively, the conveyor 4 could be fixed to
the shaft 300, with the entire shaft and conveyor being movable axially
relative
to the hopper 16.
The spring 302 acts to push the conveyor :l forwards, i.e. toward the
nozzle 10. This causes the tapering part 36,38 to come into closest adjacency
with the tapering second part 20 of the passage but if the conveyor 4 moves
axially away from the nozzle I0, the separation between the flight 24 and the
second part 20 would increase by virtue of the tapers of both. This allows
blockages to be simply removed or avoided, in a manner which will be
described in more detail below. It can be seen from the drawings that in this
example, both tapers are substantially to the same degree but could be
different.
It will be apparent to the skilled man that as the conveyor 4 slides along
the shaft 300, some provision may be required to prevent waste material being
compacted into gaps formed as the conveyor moves, which might prevent the
conveyor moving back again. Appropriate sheaths or gaskets could be used, or
the various components could comprise telescoping shields which ride over
each other and deflect waste material away from the central axis, to prevent
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8
fouling.
Figs. 1 and 2 also show an adjustable cutting plate 220 having a cutting
edge adjacent the screw at the beginning of its tapering portion. A
cooperating
cutting edge is formed along the outer edge of the conveyor flight in the
tapering part 36,38 of the conveyor, as indicated at 304, which shows a
serrated
edge extending around substantially one complete turn of the screw. The
blades 220,304 cooperate together to cut up long items such as wooden poles
and the like as they pass through the apparatus and also to serrate large,
bulky
or incompressible items, to help prevent blockages. The provision of the edge
304 along a significant length of the screw 4 ensures that the blades 220,304
can cooperate over substantially the whole range of axial positions likely to
be
occupied by the screw conveyor 4 during use. However, it will be apparent that
by virtue of the taper on the conveyor 4, the separation of the blades 220,304
will vary as the conveyor 4 moves backward and forward along the shaft 300.
The nozzle 10 will now be described in more detail with particular
reference to Figs. 4, S and 6. The nozzle 10 is coupled to the outlet end of
passage 6 at the end of section 20 and is surrounded by chamber 41 which
allows any material leaking from the nozzle 10 to be collected in the chamber
41. The nozzle is made up of two main parts 42 and 44. The first part 42 is
formed from a sheet of material such as a sheet steel with a thickness of 2 to
3mm which has been rolled up to form a cylinder and welded to maintain that
shape. The base portion 46 of the first part -12, which is connected to the
passageway 6, is circular, of substantially constant cross-section and of
unbroken sheet material. This defines a compaction chamber 200 in which
further substantial compaction of the waste material takes place upstream of
the tapering portion of the nozzle. From this base portion 46 a plurality of
e.g.
twelve fingers 48 extend, the axis of each finger initially being generally
parallel
to the longitudinal axis 50 of the nozzle 10. The width of each finger 48
decreases in the direction towards the outlet ~2 of the nozzle 10 to thereby
define V-shaped gaps (not shown) between adjacent fingers 48.
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9
The second part 44 is constructed in a similar manner to the first part
42, the two parts differing only in dimensions. In particular the second part
44
is slightly longer than the first part 42 and has a slightly larger diameter.
The
first part 42 is arranged inside the second with the base portions 46 of the
first
and second parts 42 and 44 being welded together. The two parts 42 and 44
are arranged so that the fingers 48 of one part overlap the gaps between the
fingers of the other part i.e. each finger of one part overlaps two fingers of
the
other part.
On the outer surface of the ends 54 of each of the fingers 48 of the
second outer part 44, a lug 56 is provided. These lugs ~6 extend in a
generally
outward direction. An inflatable member 306 of rubber, rubberised or other
inflatable material surrounds the outer part 44 over at least part of the
length
of~the fingers. The lugs ~6 help retain the inflatable "spring" 306 in
position
around the nozzle. The inflatable spring 306 fills a gap between the fingers
and the walls of the chamber 41, and provides resilient bias to the fingers of
the
first and second parts, to bias them to their smallest position (i.e. the
position
in which they define the smallest nozzle aperture). However, as the pressure
and/or volume of waste material passing through the nozzle 10 increases, the
cross-sectional area of the nozzle 10 can increase, for example as shown in
Fig.
6, against the resilience of the spring 306. In this instance, the inward
force
exerted by the spring 306 (reacting on the walls 41) is exceeded by the
outward
force exerted by the fingers 48 as a result of the waste material, and a new
equilibrium position is therefore established. Thus, the tapering portion of
the
nozzle 10 regulates its size in response to variations in the pressure and
volume of material passing through the nozzle and other operating conditions,
and an appropriate back pressure can be provided for satisfactory compactfon
over a range of operating conditions. The equilibrium position which is
occupied will be determined in part by the resilience of the spring 306, which
in
turn is set by the degree of inflation. As the spring 306 is further inflated,
it
becomes harder and therefore more strongly resilient, tending to hold the
nozzle more tightly with the fingers closer together. As the degree of
inflation
is reduced, the fingers are held more softly and the nozzle will tend to be
wider
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for a given set of operating conditions.
The general operation of the apparatus will now be described with
particular reference to Figs. 2 to 6. First, material is inserted into the
hopper
16. The operator then starts the motor 66 to rotate the screw conveyor 4.
Initial compaction takes place in the tapering portion of the screw, as
described
above. More substantial compacdon will then take place in the compaction
chamber 200, downstream of the end of the screw conveyor flight, between the
flight and nozzle 10. This is due to the back pressure established by the
nozzle
I0, under the variable influence of the inflatable spring 306. The action of
the
screw is to force material from a lower pressure upstream region under the
hopper, to a higher pressure region in the chamber 200. It does this by
sweeping out a void space trailing a blunt free end of the screw, which space
is
then filled by new material moving from the hopper to fill the void. Material
in
the high pressure region eventually collapses (is compacted) to become stable.
In the event that the compaction process becomes blocked for any
reason, such as an incompressible or oversized ob,~ect, the torque required to
continue turning the conveyor will increase and the thrust required to
maintain
the conveyor at a particular axial position will also increase. However, the
sliding mounting arrangement of the conveyor :1 allows the conveyor 4 to move
back from the nozzle when the back thrust is sufficient to exceed the bias
provided by the spring 302. As that happens, the gap between the conveyor
and the tapering section 20 increases, as has been described. Eventually, a
new
equilibrium position will be reached, in balance between the spring thrust and
the back thrust. This may be sufficient to allow the cause of the blockage to
pass through to the final compaction chamber 200, thereby clearing the
blockage. Similarly, if the blades 220,304 are cutting or chopping material
while the conveyor is in the forward position, but an oversize element cannot
fit bet<veen the cutting blades, the conveyor can be forced back against the
spring 302 until either the article is accommodated between the blades, so
clearing the blockage, or the cutting force bettveen the blades increases (by
virtue of the spring bias) to a degree at which the article is finally cut.
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This ability of the conveyor to be interactive to react to blockages and
move to help clear them results in a compaction apparatus which can work
more reliably with a wide range of materials and in a wide range of operating
conditions, without requiring other, more complex arrangements for clearing
blockages. The apparatus operates in a different manner to the earlier
apparatus described in the above-mentioned PCT application, in that the
present apparatus will reset itself to allow blocking material to pass through
(at
least on some occasions), rather than withdrawing the blocking material and
repeatedly presenting it until it is compacted or chopped in the intended
fashion.
Fig. 8 shows an application for a compactor of the type described,
particularly a small version having a hopper volume of approximately 0.1 and
0.4~'. In Fig. 8, a compactor 500 generally as described above is arranged
within an aesthetically pleasing housing 502 and with the axis inclined
upwardly, perhaps even vertical. A door 504 may swing down to allow material
to be introduced into the hopper through an opening 506. The compactor then
forces this material up, compacting it as it does so, into a pipe 508 which
connects the compactor 500 to a collection arrangement at ~ 10.
The collection arrangement, which may be housed in a second aesthetic
housing (not shown) whfch matches the housing 502, incorporates a carousel
having three collectfon locations 512 in the example shown. These locations
512 are equally spaced around a vertical central axis 514 and each consists of
a
basket which can hold a refuse bag or sack. Each basket 516 is supported on
the axis 514 by an arm 520. A sensor 522 associated with each arm 520
monitors the weight of the basket 516 and its contents. When the weight
exceeds a threshold, an instruction is sent to a drive arrangement 524 to
rotate
the axis X14 to bring a second, empty basket 516 to the collection position
underneath the outlet of the pipe 508. Having moved away from the collection
position, the full basket can then be emptied while the fresh, empty basket is
still receiving material through the pipe 508. It may be desirable to allow
all
except one of the baskets to be accessed for emptying, or to provide a single
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12
emptying location from which baskets may be emptied as they move to that
location.
It is preferred that the compactor operates vertically or in an inclined
direction as described, to minimise the floor space occupied by the apparatus.
Furthermore, the collection arrangement 510 allows material to be
automatically packaged into a conveniently handleable form, for instance for
manual handling. The sensor arrangement ensures that safety requirements
are not exceeded, by preventing baskets from becoming too heavy.
It will be apparent that very many variations and modifications from the
apparatus described above can be made without departing from the scope of
the present invention. In particular, the form and geometry of the hopper,
conveyor and compacting chambers described can be widely varied, as can be
the manner of mounting the conveyor for axial movement. Many alternative
designs of carousel could be designed for the apparatus of Fig. 8 and the
compactor may require some variation from the designs shown in other figures
in order to operate with a vertical rotation axis.
Whilst endeavouring in the foregoing specification to draw attention to
those features of the invention believed to be of particular importance it
should
be understood that the Applicant claims protection in respect of any
patentable
feature or combination of features hereinbefore referred to and/or shown in
the
drawings whether or not particular emphasis has been placed thereon.
