Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an endless belt
conveyor which is formed into a tubular shape to convey
materials such as powered/grained materials in an enclosed
condition, and in particular to an endless tubular belt in
which the edges are overlapped smoothly and which is
provided with holding rollers for holding the endless belt
in as near to a tubular shape as is possible, so that
sagging and twisting of the belt during running operation is
prevented.
In a conventional tubular belt conveyor, materials
to be conveyed are deposited on a flattened part of an out-
going portion of the conveyor belt, usually near the driven
roller. In order to form the flattened portion into a
tubular shape, the edges of the belt are caused to overlap
each other as the outgoing belt moves away from the driven
roller. However, at the point at which the two edges of the
belt overlap, various problems such as distortion, twisting
etc. are likely to occur. Accordingly, in conventional belt
conveyors, a pressing roller 40 (see Figure 16), which
presses one of the edges of the belt 41 downwards, has
customarily been employed to reduce these problems. As
illustrated in Figure 16, by locating a pressing roller 40
close to the point at which the two edges cross, collisions
between the two edges can be avoided. However, under these
circumstances, side-to-side movements of the belt 41, as
shown by the arrows in Figure 16, can result in slippage
and/or uneven distribution of materials wrapped in the belt
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41. Additionally, as shown by the dashed line in Figure 16,
in conventional belt conveyors, the free edge of the belt 41
frequently contacts the top of the pressing roller 40
(typically near the distal end thereof), while the other
edge of the belt 41 presses against the underside of the
pressing roller (usually in a longitudinally intermediate
portion of the roller). As a result, the frictional force
acting on the top of the roller 40 is in a direction
opposite to that of the force which acts on the underside
thereof, effectively braking the rotation of the roller 40.
The resulting friction and slippage between the pressing
roller 40 and the two edges of the belt 41 leads to
premature wear of both the roller 40 and the belt 41.
In order to avoid this problem, the pressing
roller 40 can be placed at a location remote from the point
at which the two edges cross, so that the two edges are
widely separated. However, under these conditions the belt
41 can become unduly flattened, which prevents the endless
belt 41 from being smoothly rounded.
Another disadvantage of the conventional tubular
belt conveyor is that twisting and distortion of the belt 41
can also be caused by changes in the position of materials
wrapped in the tubular belt conveyor, and further by
differences in resistance generated between the running belt
conveyor and each of the holding rollers 42. In order to
correct this twisting and distortion, a correcting roller 43
is typically provided as shown in Figure 17. However, since
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the correcting roller 43 is installed to correct the
twisting and distortion while the belt conveyor is stopped,
which is different from correcting the same problem during
running of the belt conveyor, an appropriate correction can
not be expected.
In addition, in the conventional tubular belt
conveyor, a plurality of holding rollers 42 are separately
mounted to form a hexagonal shape surrounding the belt.
Since this hexagonal shape differs substantially from a more
nearly circular shape, large resistance forces are generated
during running operation, which prevents the belt conveyor
from running smoothly.
Japanese Patent laid-open Publication 57-141304
discloses a tubular belt conveyor which also corrects the
twisting motion of the belt conveyor about an axial
direction thereof. However, in reality, during running
operation a belt will tend to twist at random locations.
Therefore, to prevent the belt conveyor of this publication
from being twisted it is necessary to provide a correcting
device to each of supporting frames, as illustrated in
Figures 17a-b.
In the tubular belt conveyor, twists about the
axis which are generated during running operation can occur
in several, generally random, locations along the belt.
Accordingly, it is difficult to select in advance positions
at which the twist preventing means, such as the pressing
roller as described above, should be set. Therefore, the
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twist preventing means must be provided on all of the
supporting frames, which means that neither the number of
the supporting frames nor the number of the twist preventing
means can be reduced, which is very wasteful. Further, the
provision of the twist preventing means is of no use in
preventing the tubular belt from sagging.
The present invention is directed to overcoming
many of the above-described drawbacks associated with the
prior art. Thus an object of the present invention is to
provide an economic tubular belt conveyor in which the
twisting of the tubular belt can be properly corrected and
sagging of the belt between the supporting frames can also
be prevented, and in which the space between the supporting
frames can be widened, so as to reduce the number of the
supporting rollers.
In order to achieve the above mentioned objects,
according to the present invention, there is provided a
tubular belt conveyor comprising: a driving roller disposed
at one end of the conveyor; a driven roller disposed at the
other end of the conveyor; an endless conveyor belt wound
around driving and driven rollers, an upper section of the
belt defining an outgoing belt and a lower section of the
belt defining a return belt; a plurality of primary support
frames substantially evenly spaced along the conveyor for
supporting the outgoing and return belts; deformation means
disposed proximal each of the driving and driven rollers,
for deforming both of the outgoing and return belts into a
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tubular shape, the outgoing and return belts being flattened
to pass around the driving and driven rollers, whereby
materials to be conveyed are placed on a flattened portion
of the outgoing belt prior to deformation of the outgoing
belt into a tubular shape by the deforming means, and the
materials are conveyed in the wrapped condition; and guiding
means disposed near the deformation means for guiding the
edges of both the outward and return belts, the guiding
means including at least one pressing roller comprising two
or more respective roller elements disposed along a common
axis, each roller element being independently rotatable with
respect to adjacent roller elements.
In an embodiment of the present invention, the
pressing roller is located proximal a location where the
opposite edges of the belt intersect and overlap.
Preferably, the pressing roller presses on one of the edges
of the belt, so as to force that edge under the other edge
of the belt. In one embodiment of the invention, the
pressing roller includes and inboard roller element for
pressing on an edge of the belt, and an outboard roller
element for contacting the other edge of the belt. Since
the inboard and outboard roller elements are independently
mounted, the can readily rotate in opposite directions under
the frictional forced imposed on them by the respective
edges of the belt. In another embodiment of the present
invention, the pressing roller comprises a plurality of
narrow roller elements, each of which are independently
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mounted for rotation. This arrangement increases
flexibility, and allows the pressing roller to function
properly even if the edges of the belt shift laterally
during operation of the conveyor.
In an embodiment of the present invention, each of
the primary support frames includes an upper passage through
which the outgoing belt passes, and a lower passage through
which the return belt passes, the upper and lower passages
including a plurality of respective support rollers arranged
in an polygonal configuration. Preferably, six support
rollers arranged in a hexagonal configuration are used. In
this case, the support rollers of one primary support frame
are rotated with respect to the support rollers of the
adjacent primary support frames. This prevents the belt
from adopting the overall shape of the support rollers, and
thus ensures that the belt retains a smoothly rounded shape.
In an embodiment of the present invention,
secondary support rollers are arranged horizontally under
the outgoing and return belts, approximately midway between
each of the primary support frames. The secondary support
rollers serve to prevent sagging of the belt between the
primary support frames. Preferably, the angle of the
secondary support rollers, with respect to the running
direction of the belt, can be adjusted. This allows the
secondary support rollers to also serve to counteract any
twisting of the belt. Preferably, the angle of the
secondary support roller can be adjusted while the belt is
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running, so that any twisting of the belt can be accurately
corrected, without interrupting operation of the conveyor.
In an embodiment of the present invention, when
the conveyor follows a transversely bent path, vertically
oriented bending rollers are arranged close to the secondary
support rollers, on the inside of transversely bent portion
of the belt. The bending rollers serve to maintain the
running belt in a smoothly bending path between the primary
support frames. Preferably, the angle of the bending
rollers, with respect to the running direction of the belt,
can be adjusted. This allows the bending rollers to also
serve to counteract any twisting of the belt. Preferably,
the angle of the bending rollers can be adjusted while the
belt is running, so that any twisting of the belt can be
accurately corrected, without interrupting operation of the
conveyor. By this means, in the bent portion of the
conveyor, both secondary support rollers and bending rollers
can be used to counteract twisting of the belt.
The invention will be more readily understood from
the following description of a preferred embodiment thereof
given, by way of example, with reference to the accompanying
drawings, in which:
Figure 1 shows a side view of a tubular belt
conveyor according to an embodiment of the present
invention;
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Figure 2 shows a plan view of a tubular belt
conveyor according to an embodiment of the present
invention;
Figure 3 shows a front view of an upper half of a
pressing frame illustrating a pressing roller in accordance
with an aspect of the present invention;
Figure 4 shows a longitudinal cross-section view
of the pressing roller illustrated in Figure 3;
Figure 5 shows a partial cross-section view of
another pressing roller in accordance with an aspect of the
present invention;
Figure 6a shows a cross-section view of the
tubular belt conveyor cut along line V - V shown in Figure
l;
Figure 6b shows a cross-sectional view of the
tubular belt conveyor cut along line VI - VI shown in Figure
l;
Figure 7 shows a perspective view of a portion of
a belt conveyor according to the present invention, showing
a four successive sets of primary supporting rollers;
Figure 8 shows a side view of a tubular belt
conveyor in accordance with a second embodiment of the
present invention;
Figure 9 shows a plan view of the tubular belt
conveyor of Figure 8;
Figure 10 shows a cross-section view of the
tubular belt conveyor of Figure 8, cut along line A - A;
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Figure 11 shows a cross-section view taken along
line B - B in Figure 8;
Figure 12 shows a plan view seen from a direction
of line D - D in Figure 11;
Figure 13 shows a cross-section view taken along
line C - C in Figure 8;
Figure 14 shows a plan view of a portion of the
belt conveyor of figure 9;
Figure 15 is a side view seen from a direction of
the line E - E in Figure 14.
Figure 16 shows a cross-section view of a
conventional tubular belt conveyor, illustrating a
conventional pressing roller;
Figure 17a shows a partial cross-sectional plan
view of a twist preventing device of a conventional tubular
belt conveyor; and
Figure 17b shows a partial cross-sectional side
view of the twist preventing device shown in Figure 17a.
Figures 1 and 2 respectively show side and plan
views of an embodiment of a tubular belt conveyor
according to the present invention. The conveyor
generally comprises an endless belt 2 composed of flexible
material which extends along the length of the conveyor 1
and around a drive roller 3 and a driven roller 4. As
illustrated in Figures 1 and 2, the conveyor 1 is divided
into two transition zones 7a located at opposite ends of the
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conveyor 1, and an intermediate zone extending between the
transition zone. Within the intermediate zone, which makes
up most of the length of the conveyor 1, the endless belt 2
is maintained in a substantially tubular shape. Within the
two transition zones, the belt 2 transitions from the
tubular shape of the intermediate zone to a flat shape as it
passes around the drive and driven rollers 3 and 4. Within
the intermediate zone, the belt 2 is supported by primary
support rollers 5 operatively mounted on primary support
frames 6 disposed at predetermined intervals along the
length of the conveyor 1. The transition zones 7a, 7b are
defined between each of the drive and driven rollers 3, 4,
and the nearest primary support frame 6, in which the belt
2 is deformed from a flattened shape into a substantially
tubular shape, and vis-a-verse. In order to support the
belt 2 within each transition zone 7a, 7b, and to assist in
the smooth deformation of the belt 2, one or more sets of
transition rollers 8 are provided on suitable transition
support frames 9. A pressing frame 10 having a pressing
roller 11 is provided within each transition zone 7a, 7b to
ensure that the opposite edges 2a, 2b of the endless belt 2
overlap each other smoothly.
In operation, the drive roller 3, which is driven
by a suitable drive means (not shown), frictionally engages
the endless belt 2 and causes the belt 2 to run continuously
in the direction of the arrows in Figure 1. As illustrated
in Figure 1, the belt 2 passes around the driven roller 4
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and into a transition zone 7a in which the belt is gradually
deformed by the transition rollers 8 and pressing rollers 11
until the edges 2a, 2b of the belt 2 overlap to define a
tubular shape. Within the transition zone 7a, a hoper 12
deposits material to be transported 13 onto the belt 2. By
this means, the material 13 is substantially enclosed by the
belt 2 shortly after being deposited on the belt 2. The
material 13 is transported along the length of the conveyor
1, in a substantially enclosed condition, to the transition
zone 7b near the drive roller 3. As the belt 2 approaches
the drive roller 3, the transition rollers 8 cause the belt
2 to smoothly transition to a flattened condition, thereby
effectively "unwrapping" the material 13 being transported.
As the belt 2 passes around the drive roller 3, the material
13 is deposited from the belt 2 into a receiving tub 14.
From the drive roller 3, the belt passes through the
transition zone 7b and returns to the driven roller 4 in a
tubular condition. One or more tensioning or idler rollers
15 can be provided near the drive roller 3 to adjust belt
tension and/or the angle of engagement between the belt 2
and the drive roller 3.
In the remaining discussion, the portion of the
belt 2 travelling from the driven roller 4 to the drive
roller 3, and on which the material 13 is transported, will
be referred to as the outgoing belt 2'. Conversely, the
portion of the belt 2 travelling from the driven roller 4 to
11
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the drive roller 3 will be referred to as the return belt
2''.
Figure 3 illustrates a portion of a pressing frame
10 disposed in the transition zone 7a near the driven roller
4. The pressing frame 10 is divided into an upper passage
through which the outgoing belt 2' passes, and a lower
passage (not shown), through which the return belt 2''
passes. The pressing frame 10 is located in the transition
zone 7a, at or near the point at which the opposite edges
2a, 2b of the outgoing belt 2' overlap. The pressing roller
11 is composed of an inboard roller unit 16, and an outboard
roller unit 17, both of which are independently mounted on
bearings for rotation about a common shaft 18 (see Figure
4). The shaft 18 is conveniently affixed (for example by
welding) to a mounting plate 19 having a plurality of
mounting plate slots 20. A corresponding mounting bracket
21 affixed to the pressing frame 10 is provided with a
plurality of mounting bracket slots 22, whereby the pressing
roller can be conveniently affixed to the pressing frame by
means of bolts passing through the slots 20 and 22.
Preferably, the slots 20 of the pressing roller mounting
plate 19 are provided at right-angles to the slots 22 of the
mounting bracket 21, so that the angle and the position (in
both the vertical and lateral directions) of the pressing
roller can be adjusted.
The pressing roller 11 is mounted so that the
inboard roller unit 16 applies pressure to a first edge 2a
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of the belt 2' while the opposite edge 2b is being guided
over it. At this point, the opposite edge 2b tends to drop
(due to gravity and tension within the belt) onto the upper
portion of the pressing roller 11, and contacts the outboard
roller unit 17. Since the two roller units 16, 17 are
independently mounted, they can rotate freely in opposite
directions due to friction with the respective edges 2a, 2b
of the belt 2', thereby minimizing frictional forces between
the pressing roller 11 and the opposite edges 2a-b of the
belt 2'.
In cases where the specific gravity of the
material 13 being conveyed is large, it is preferable to
support the belt 2' by means of a plurality of receiving
rollers 23 operatively mounted to the pressing frame 10 as
shown in dotted lines in Figure 3.
During running operation of the conveyor 1, the
specific locations of the edges 2a, 2b of the belt 2' can
change. As a result of this, it can be difficult to predict
the best position of the pressing roller 11 so that one edge
2a contacts only the inboard roller unit 16, while the other
edge 2b contacts only the outboard roller unit 17. Figure
5 illustrates an embodiment of the pressing roller 11 which
substantially overcomes this difficulty. In this
embodiment, the inboard and outboard roller units 16, 17 are
replaced by a plurality of narrow roller units 24, each of
which are independently mounted on bearings for rotation
about the common shaft 18. This arrangement provides
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CA21 09769
maximum flexibility in the placement of the pressing roller
11, and allows the edges 2a, 2b of the belt 2' to move
during operation of the belt, while the probability of both
edges simultaneously engaging the same roller unit 23 is
minimized.
As mentioned previously, the endless belt 2 is
substantially tubular in shape along most of the length of
the conveyor 1, and transitions to a flat shape at either
end of the conveyor 1 (i.e. as it passes around the drive
and driven rollers 3 and 4). Between the transition zones
7a, 7b, the belt 2 is maintained in a tubular condition, and
is supported by primary support rollers 5 operatively
mounted on primary support frames 6 disposed at
predetermined intervals along the length of the conveyor 1.
lS Each primary support frame 6 is provided with an
upper passage through which the outgoing belt 2' passes, and
a lower passage through which the return belt 2'' passes.
A respective set of primary support rollers 5 is operatively
disposed within each of the upper and lower passages of the
primary support frame 6. As illustrated in Figures 6a and
6b, each set of primary support rollers 5 comprises a
plurality of rollers 5a-f which are arranged to form a
polygonal configuration surrounding the belt 2 on all sides.
Figures 6a and 6b show two orientations of the
primary support rollers 5a-f within the primary support
frame 6 (i.e. hexagonal arrangements rotated 30~ with
respect to each other). In order to maintain the belt 2 in
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as close to a cylindrical shape as possible, it is
preferable to alternately use both orientations in
successive support frames along the length of the conveyor
1. Thus the orientations of the primary support rollers 5
will preferably alternate along the length of the conveyor
1 in the manner illustrated in Figure 7.
The primary support frames 6 are conveniently
supported and linked longitudinally by structural elements
25 extending along substantially the whole length of the
conveyor 1. Conveniently, through most of the length of the
conveyor 1, the spaces between the primary support frames 6
will be substantially equal. However, in order to ensure a
smooth entry (and exit) of the tubular belt 2 into (and
from) the transition zones 7a-b, the spaces between the
primary support frames 6 can advantageously be reduced near
the transition zones 7a-b.
Next, torsion correcting means for appropriately
correcting twisting phenomenon of the tubular belt conveyor
and means for reducing the number of supporting rollers
according to the present invention will be described.
Figures 9 and 10 generally show an example of the
tubular belt conveyor according to the present invention.
In the side view of Figure 9 the tubular belt conveyor 1 is
shown linearly inclined from the driven roller 4 end toward
the driving roller 3 end. On the other hand, in the plan
CA21 09769
view of Figure 10 the conveyor 1 is shown partially curved
in a transverse direction. In other respects, the general
lay-out and operation of the conveyor 1 is similar to that
Figure 1, and thus will not be discussed in further detail
here.
As shown in Figure 11, in this example the
supporting frame 6 is partitioned into upper and lower
sections by a central partition member 6a, and central
longitudinal structural elements 26 are mounted in the
vicinity of the partition 6a in addition to the structural
elements 25 described above.
Figure 12a shows a cross-sectional view through
the conveyor 1 at a location approximately midway between
successive primary support frames 6, within a straight
portion of the conveyor 1. A horizontally disposed
secondary support roller 27 supports the outgoing belt 2',
and is mounted on secondary support brackets 28, which are
in turn affixed to the central longitudinal structural
elements 26. A similar secondary support roller 27 supports
the return belt 2'', and is mounted on support brackets 28a
affixed to the structural elements 25. The secondary
support rollers 27, 27a serve to support the belt 2 between
the primary support rollers 5. This helps prevent sagging
of the belt, and allows the support frames to be spaced
further apart (for example, a conventional spacing of 1.5m
can be increased to approximately 2.0 to 2.5m).
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In order to correct undesired twisting of the belt
2, the brackets 28, 28a supporting the secondary support
rollers 27 are affixed to the structural elements 25, 26 by
means of mounting bolts 29. The mounting brackets 28, 28a
are provided with elongated mounting slots 30, as
illustrated in Figure 13, through which the mounting bolts
29 pass. By means of the elongated mounting slots 30, the
angle of the secondary support rollers 27, can be adjusted
with respect to the direction of travel of the belt 2, as
shown in Figure 13. As the belt 2 runs over the angled
roller 27, a twisting force F produced by friction between
the belt 2 and the roller 27 is applied to the belt 2 in a
direction determined by the direction of the angle of the
roller 27. Thus during operation of the conveyor 1, any
twist in the belt at a particular location can be corrected
by suitably adjusting the angle of the supporting roller 27
nearest to that location, without interrupting the running
operation of the conveyor 1.
Figure 14 shows a cross-sectional view through the
conveyor 1 at a location approximately midway between
successive primary support frames 6, within a curved portion
of the conveyor 1. In addition to the horizontally arranged
secondary support rollers 27, vertical bending rollers 31
are mounted on respective bending roller support brackets 32
affixed to the structural elements 25, 26. As shown in
Figure 15, the bending rollers 31 are located on the inside
of the curve of the belt 2, and helps to maintain a smooth
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curve in the belt as it moves through the bend. In Figure
15, the solid and dashed lines respectively indicate the
path of the belt 2 with and without the bending roller 31.
By maintaining a smoothly rounded curve between the primary
support frames, the bending roller 31 reduces the running
resistance of the belt 2.
The vertical bending rollers 31 are preferably
mounted in a manner similar to that of the secondary support
rollers 27. This allows the angle of the bending rollers 31
to be adjusted as shown in Figure 16. Thus in the curved
portions of the conveyor 1, both the secondary support
rollers 27 and the ending rollers 31 can be used to
counteract any tendency of the belt 2 to twist. This allows
any twisting tendency of the belt to be accurately
counteracted,without interrupting running operation of the
conveyor.
The present invention has been described with
reference to the preferred embodiments. However, the
present invention is not limited thereto and many variations
and modifications of the invention can be practised upon
consideration of the foregoing disclosure without departing
from the scope and spirit of the appended claims.
