Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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RETLR' ROLLER ASSEViBLY
FOR .~ BL-L.K COr'''EYOR
Ronald G. .anderson
TECH~'ICAL FIELD
The invention relates to a return roller assembly for the return flight of the
continuous conveyor belt of a bulk conveyor, and more particularly to such an
assembl comprising three rollers arranged to define a supporting shape
accommodating the shallow. inverted, trough-shaped set of the return flight.
BACKGROL~:~iD ART
While not necessarily so limited. the present invention is particularly .
l~ applicable to heavy duty bulk conveyors of the type used to transport
gravel,
aggregate. coal and the like. Such conveyors can be of any length, and in some
applications can extend several miles. The bulk conveyor is provided with a
continuous belt which can travel at speeds of from about 300 to about 1100
feet
per minute.
Bulk conveyors of the type just described are well-known in the art.
Generally, the bulk conveyor comprises a roller supporting framework having
side
members and appropriate transverse bracing. The roller supporting framework
is,
itself, normally supported at a com-enient height by legs depending downwardly
from the framework side members. Alternatively, the frameword could be
suspended from an appropriate overhead structure. The upper flight of the
continuous belt is supported at appropriate intervals by troughing roller
assemblies
so configured and arranged as to impart to the upper flight a transverse,
trough-
like cross section. The lower flight of the continuous belt is normally
supported at
appropriate intervals by single rollers extending transversely across the
framework.
The present invention is directed to improved support for the return flight
of the continuous conveyor belt. Prior art single, transverse, support rollers
for
the return flight are characterized by a number of problems. At times,
problems
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are encountered with the belt not tracking properly,
resulting in damage to the return rollers, the framework,
and the belt. The relatively long return rollers are shaft
mounted, and are subject to shaft deflection resulting in
reduced bearing life. Finally, it has been found that the
troughing rollers supporting the upper flight and imparting
a trough-like cross section to the upper flight, actually
tend to impart a shallow, trough-like, transverse "set" to
the belt so that the lower flight is characterized by an
inverted, shallow, trough-like transverse cross-section. As
a result, the longitudinal edges of the belt tend to cut
into the return rollers markedly shortening the roller life
and damaging the belt edges.
The present invention is based upon the discovery
that the above-noted problems in association with the return
flight can be overcome by substituting for each single
return roller an assembly of three shorter rollers arranged
to define a supporting shape accommodating the shallow,
inverted, trough-like set of the return flight. Guidance of
the belt and tracking of the belt are markedly improved.
Shaft deflection characteristic of long rolls is eliminated.
Furthermore, in the new assembly, six bearings carry the
same load as was carried by two bearings when the long
single roll was used. Both of these advantages greatly
lengthen the bearing life. Roll cutting by the conveyor
belt longitudinal edges is eliminated. In some instances,
the entire return roll assembly may be rotatively mounted at
its vertical centerline for very limited pivotal movement,
as will be described hereinafter. This slight pivotal
movement will tend to cause the return flight to be self-
centering.
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SUMMARY OF THE INVENTION
According to the invention there is provided a
return roller assembly for the return flight of the
continuous belt of a bulk conveyor, the return flight
traveling in a longitudinal direction of travel, said return
roller assembly comprising a center roller and a pair of end
rollers with respect to the longitudinal direction of
travel, said center roller having first and second ends and
being mounted on a shaft, said center roller being disposed
generally horizontally, each of said end rollers being shaft
mounted and having an inner end and an outer end, the
uppermost part of the inner ends thereof are at the same
vertical level as the uppermost part of said center roller,
and the uppermost part of the outer ends of said end rollers
are below said vertical level, said center and outer rollers
defining a shallow, inverted, trough-like supporting shape
for said return flight.
The return roller assembly is preferably mounted
for slight pivotal movement about the vertical centerline of
the assembly. This slight pivotal movement tends to
automatically maintain the return flight of the conveyor
belt centered with respect to the conveyor.
The invention also provides a bulk conveyor
comprising an elongated framework, said framework comprising
side members joined together at intervals by cross braces,
said framework being supported at intervals along its
length, a continuous, driven conveyor belt having an upper
flight and a lower return flight, said framework having
support means thereon for the upper flight and the lower
return flight of said conveyor belt, said support means for
said conveyor belt upper flight comprising a plurality of
troughing idler roller assemblies mounted at intervals along
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said framework and transversely thereof, said troughing
roller assemblies being oriented to impart to said upper
conveyor belt flight a trough-like transverse cross
sectional shape, said lower return flight of said conveyor
belt having a shallow, inverted, trough-shaped set, said
support means for said lower return flight comprising a
plurality of return roller assemblies extending transversely
of said frame at intervals therealong, each of said return
roller assemblies comprising a first end roller, a central
roller and a second end roller extending transversely across
said conveyor framework, a shaft mounting said center
roller, said center roller having first and second ends,
means for mounting said center roller shaft horizontally, a
shaft mounting each of said end rollers, each end roller
having an inner end and an outer end, means mounting said
shafts of said end rollers such that the uppermost portion
of the inner ends thereof are at the same vertical level as
the uppermost part of said center roller, and the uppermost
part of the outer ends of said end rollers are below said
vertical level, said center and end rollers defining a
shallow, inverted trough-like supporting shape for said
lower return flight.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a fragmentary perspective view
illustrating a conventional prior art bulk conveyor.
Figure 2 is a fragmentary perspective view,
similar to Figure 1, and illustrating a bulk conveyor
provided with a return roller assembly of the present
invention.
Figure 3 is a plan view of the return roller
assembly of the present invention.
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Figure 4 is an elevational view as seen from the
bottom of Figure 3.
Figure 5 is an end elevational view as seen from
the right side of Figure 3.
Figure 6 is a fragmentary plan view, similar to
Figure 3, illustrating another embodiment of the present
invention.
Figure 7 is a fragmentary elevational view as seen
from the bottom of Figure 6.
Figure 8 is an end elevational view as seen from
the right of Figure 6.
Figure 9 is a fragmentary elevational view, partly
in cross section, of the central pivot assembly of Figures 6
and 7.
Figure 10 is a fragmentary elevational view,
partly in cross section, of one of the support rollers of
Figure 6.
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DETAILED DESCRIPTION OF THE INVENTION
Reference is first made to Figure 1 wherein an exemplary prior art bulk
conveyor is fragmentarily illustrated. The conveyor is generally indicated at
1 and
ce.~mprises a tramework generally indicated at 2. The framework comprises side
members 3 and 4 which extend the length of the conveyor. The side members 3
and 4 are joined together by appropriate tramverse braces, one of which is
illustrated at 5. The framework ? is located at a convenient height by a
plurality
of legs affixed to side members 3 and 4. Two such legs are shown at 6 and 7.
The conveyor 1 is provided with a continuous belt 8. The belt has an
upper tlight 8a and a lower flight 8b. At appropriate intervals along the
length of
the conveyor, the upper flight 8a of conveyor belt 8 is supported by an
assembly
of troughing rollers. The troughing roller assembly is generally indicated at
9 and
comprises a center roller 10 and end rollers 11 and 12. The rollers 10, 11 and
12
are idler rollers, each rotatively mounted on its own shaft and provided with
appropriate bearing means (now shown). The shaft 13 of roller 10 is supported
by
a pair of brackets 14 and 15 mounted on the transverse brace 5. It will be
noted
that the roller 10 and its shaft 13 are horizontal. The roller 11 is aligned
with the
roller 10, but its shaft 16 slopes upwardly and outwardly from roller 10,
being
supported by a bracket 17 mounted on transverse brace 5 and a bracket 18
affixed
to side member 3. In a- similar fashion, the roller 12 is aligned with the
roller 10
and its shaft 19 extends upwardly and outwardly from roller 10, being
supported
by a bracket 20 affixed to transverse brace 5 and a bracket 21 affixed to side
member 4.
It will be immediately apparent that the orientation of rollers 10, 11 and 12
impart a trough-like transverse configuration to the upper flight 8a of
conveyor
belt 8. This, of course, enables the upper flight to more easily transport
material
such as aggregate, gravel, coal or the like. The rollers 11 and 12 slope
upwardly
and outwardly with respect to the horizontal and the angularity of this upward
and
outward slope may vary, depending upon the material being conveyed, the nature
of the belt, the speed of the belt and the like. Normally, the angularity of
rollers
11 and 12 to the horizontal will fall within the range of from about 27' to
about
45'
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The lower flight 8b of the conveyor belt 8 is supported at appropriate
inters a(s along the conveyor 1 by a plurality of single rollers, one of which
is
chown in FiQUre 1 at _'''. The roller ?2 is rotatively mounted on a shaft 23
and is
provided with appropriate bearings (not shown). The ends of the shaft 23 are
supported by brackets 2.1 and ?~ which depend downwardly from side members 3
and 4. respectively.
The prior art structure described with respect to Figure 1 functions well
and properly, but is characterized by problems relating to the roller 22.
First of
all, since the roller is of a length sufficient to extend across the conveyor
l, it is
subject to shaft deflection common to long rollers. This, in turn, means
shorter
bearing life. Furthermore, the weight of the return flight is supported by the
two
bearings (not shown) located within the ends of the roller 22.
It has been found that the assemblies of troughing rollers 10, 11 and 12
impart to the belt 8 a permanent, shallow, inverted, trough-shaped "set" which
is
clearly shown in Figure 1 with respect to the bottom flight 8b. As a
consequence,
the return flight 8b is primarily supported along its longitudinal edges by
roller 22.
This not only causes undue wear of the conveyor belt edges, but also wear of
roller 22, the conveyor belt edges tending to cut into the roller. This wear
can
become sufficiently pronounced that the roller 22 must be replaced. Finally,
the
single, horizontally oriented roller 22 provides little or no tracking control
of the
lower flight. The conveyor belt 8 is generally made up of segments, including
replacement segments. Sometimes, proper alignment of segments is not achieved
at the junctures thereof, which will adversely affect the tracking
characteristics of
the conveyor belt. Sometimes a replacement segment is not exactly the same as
the belt in which it is inserted, and this too will adversely affect the
tracking
c haracteristics.
It will be understood that the prior art conveyor 1 of Figure 1 is exemplary
only. The construction and nature of the framework 2, the legs 6 and 7 and the
mounting means for troughing rollers 10, 11 and 12 and return roller 22, all
may
differ from one installation to another. The precise construction of these
elements,
however, does not constitute a limitation of the present invention. For
example,
in Figure 1, the arrows A and B illustrate the direction of travel of the
upper flight
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'''' 6
Qa and the lower flight 8b respectively, of the conveyor belt 8. The troughing
o t lers 10. 11 and 12 are shown in alignment across the conveyor 1. It is a
~:~mmon practice to locate the horizontal roller 10 rearwardly of the upwardly
and
~~utwarcilv sloping rollers 11 and 12 and to align the inner ends of the
rollers 11
and 1 ~ with the ends of the horizontal roller 10. This type of construction
enables
;realer roller length and eliminates gaps.
Reference is now made to Figure 2. For purposes of an exemplary
showing, Figure 2 illustrates a conveyor identical to that of Figure 1 with
the
exception that it is provided with return roller assemblies of the present
invention
for support of the return tlight of the conveyor belt. In Figure 2, like parts
have
been given the same index numerals used in Figure 1.
Figure 2 illustrates a return roller assembly of the present invention,
Qenerally indicated at 26. Ic.will be understood by one skilled in the art
that
return roller assemblies of the type shown at 26 will be provided at
appropriately
spaced intervals along the length of the conveyor to properly support the
conveyor
belt lower return flight Sb.
The return roller assembly 26 comprises an elongated support 27 mounted
on and between a pair of brackets 28 and 29 which are affixed to and which
depend downwardly from the conveyor side members 3 and 4. The roller
assembly 26 further comprises a central horizontal roller 30 rotatively
mounted on
a shaft 31 which, in turn, is supported by brackets 32 and 33 extending from
one
side of elongated support 27. A pair of downwardly and outwardly sloping
rollers
34 and 35 are rotatively mounted on shafts 36 and 37, respectively. The shaft
36
of roller 34 is supported by brackets 38 and 39 affixed to elongated support
27.
Similarly, the shaft 37 of roller 35 is supported by brackets 40 and 41
affixed to
the elongated support 27. It will be noted that brackets 38 and 39 of roller
34 and
brackets 40 and 41 of roller 35 extend from the side of elongated support 27
opposite the side from which the brackets 32 and 33 of roller 30 extend. As is
apparent from Figure 2, the central roller 30 is mounted on the upstream side
of
support 27 and rollers 34 and 35 are mounted on the down stream side of
support
27 with regard to the direction of travel B of the conveyor belt lower return
flight 8b.
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Reference is now made to Figures 3, 4 and 5 wherein the return roller
assembly 26 is more clearly shown. The elongated support 27 may have any
appropriate cross sectional configuration. For example, it may constitute a
tubular
member of rectangular cross section, an I-beam or a channel member, as shown
in
Figure ~.
The rollers 30. 34 and 3~ are rotatively mounted on their respective shafts
31, 36 and 37 by appropriate bearing means (not shown). While not so limited.
the rollers 30. 34 and 35 are preferably of the same length, and may have a
length
ranging from about 8 inches to about 28 inches, depending upon the width of
the
conveyor belt being supported. Depending upon their length, the rollers 30, 34
and 35 may have a diameter ranging from about 4 inches to 6 inches, the
diameter
increasing as the length increases. The hubs of the rollers may be provided
with
3/4 inch tapered roller bearings. The shafts 31, 36 and 37 are fixedly mounted
in
their respective brackets 32-33, 38-39, and 40-41. As is most clearly shown in
Figure 5, the shaft supporting brackets 32, 33, 38, 39, 40 and 41 are
generally L-
shaped, one leg of each bracket being welded or otherwise appropriately
attached
to the elongated support 27. The brackets 32 and 33 are so sized and shaped
that
the shaft 31 and its roller 30 are horizontal. The brackets 39 and 40, which
support the shafts 36 and 37 at the innermost ends of their respective rollers
34
and 35 are so sized and configured that the highest part of the rollers 34 and
35, at
the innermost ends thereof, lie at the same vertical level as the highest
portion of
center roller 30. This is clearly shown in Figures 4 and 5. It will further be
noted from Figures 3 and 4 that the innermost ends of rollers 34 and 35
slightly
overlap the ends of horizontal roller 30, as viewed in Figure 4, such that in
the
elevational view of Figure 4, there is no apparent longitudinal gap between
rollers
30, 34 and 35. The brackets 38 and 41, supporting the outermost ends of shafts
36 and 37, are so sized and configured that the outermost ends of the rollers
34
and 35 are lower than their innermost ends, resulting in the fact that the
rollers 34
and 35 slope downwardly and outwardly with respect to horizontal roller 30.
This
is clearly seen in all three of Figures 3, 4 and 5. The brackets 38, 39, 40
and 41
are welded or otherwise appropriately affixed to that side of elongated
support 27
opposite the side to which brackets 32 and 33 are affixed. Furthermore, the
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hrackets 38, 39, 49 and 41 are slightly tilted so as to be substantially
perpendicular to the respective one of shafts 36 and 37 they support.
It will be apparent, particularly from Figure 4, that the return assembly
rollers 30. 34 and 35 define a supporting shape for the return flight 8b of
the
conveyor belt 8; which accommodates the shallow, inverted, trough-shaped set
of
lower flight 8b. As noted above, the angular arrangement of troughing rollers
10.
11 and 12 imparts a trough-Nice configuration to the conveyor belt upper
flight 8a
so that it can more easily convey bulk material. The angular relationship of
the
return rollers 30, 34 and 35 of the present invention is intended to
accommodate
the shallow. trough-shaped set of the conveyor belt lower flight 8b. It has
been
found that the return roller assemblies of the present invention provide
markedly
improved guidance for the conveyor belt lower flight 8b. This, in turn,
results in
better tracking of lower flight 8b. In addition, each roller having bearing
means at
each end, six bearings carry the same load as two bearings in the return
roller 22
of Figure 1. This greatly reduces bearing wear. In addition, shaft deflection
characteristic of long rollers is eliminated by the provision of three shorter
rollers,
also increasing bearing life. Finally, the fact the rollers 30, 34 and 35 are
so
angular related as to accommodate the set of lower flight 8b, causes the lower
flight to be support substantially throughout its lid, rather than primarily
at its
longitudinal edges. As a consequence, the roller edges do not cut into the
rollers
34 and 35, increasing roller life and greatly reducing wear of the conveyor
belt at
its longitudinal edges.
It has been found that as the angularity of troughing rollers 11 and 12
increases from the horizontal, imparting a deeper trough-like cross sectional
configuration to the conveyor belt upper flight 8a, the greater will be the
trough-
like set in the conveyor belt lower return flight 8b. As a consequence, the
greater
the angularity of shafts 16 and 19 of troughing rollers 11 and 12, the greater
should be the angularity of the shafts 36 and 37 of return rollers 34 and 35.
While not necessarily so limited, in most instances the angularity of return
roller
shafts 36 and 37 will fall within the range of from about 3' to about 6' from
the
horizontal.
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In the embodiment of Figures 2 through ~, the center horizontal roller 30 is
located behind the end rollers 34 and 3~ from the standpoint of the lower
flight
direction of movement indicated by arrow~B. It would be within the scope of
the
invention to have the rollers 30. 34 and 35 so supported that their shafts are
S aligned transversely of the conveyor. as are the shafts 13, 16 and 19 of the
troughing rollers 10. 11 and 12. However, the arrangement illustrated is
preferred
because it allows for greater roller length and there is, as viewed in Figure
4, no
Qap in the supporting profile defined by rollers 30, 34 and 35.
The brackets 28 and 29 are preferably adjustable with respect to. side
frames 3 and 4. This enables adjustment of the transverse angular relationship
of
the roller assembly 26 to the lower return flight 8b.
Reference is now made to Figures 6-10 wherein a second embodiment of
the return roller assembly of the present invention is illustrated. Referring
first to
Figures 6, 7 and 8, this second embodiment of the return roller assemhly is in
many respects similar to the embodiment of Figures 2-S, and like parts have
been
given like index numerals. The second embodiment is generally designated at
26a
and comprises an elongated support 27a similar to the elongated support 27 of
Figures 2-5 with certain exceptions. First of all, the ends of the elongated
support
27a are not affixed to framework support brackets 28 and 29 (see Figure 2),
but
rather are slightly spaced inwardly from these brackets. It will be noted that
while
the elongated support 27a is slightly shorter than the elongated support 27 of
Figures 2-5, it again is illustrated as being made of a channel member having
a
top portion and downwardly depending sides.
One side of the elongated support 27a mounts the brackets 32 and 33 to
which the shaft 31 of horizontal roller 30 is affixed. Similarly, the opposite
side
of elongated support 27a mounts brackets 38 and 39'to which the shaft 36 of
end
roller 34 is affixed. The same side of the elongated support 27a mounts
brackets
40 and 41 to which the shaft 37 of end roller 35 is affixed.
In this embodiment, there is a fixed elongated support 42 of any
appropriate cross section. For purposes of an exemplary showing, it is
illustrated in
Figure 8 as being a channel member, having a top portion and downwardly
depending
sides, similar to the elongated
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support Z7a. The fixed elongated support 42 will have its ends affixed to the
downwardly depending brackets 28 and 29 of Figure 2, in substantially the same
way shown in that Figure with respect to elongated support 27.
The elongated support 27a is pivotally mounted to the fixed
elongated support 42. This pivotal mounting is located at the longitudinal
censers
of elongated supports 27a and 42 and is generally indicated at 43 in Figures 6
and 7.
The pivotal mounting 43 is more clearly shown in Figure 9. A cylindrical
stud 44 is welded or otherwise appropriately affixed to the top surface of the
LO fixed ; elongated support 42 at the longitudinal and transverse center
thereof. A
bearing block 45, containing an appropriate bearing diagrammatically indicated
at
46, is affixed to the two downwardly depending sides of elongated support 27a,
and is adapted to receive the stud 44 to complete the pivotal connection of
elongated support 27a to elongated support 42.
Near its ends, the elongated support 27a is provided with stabilizing
support roller assemblies to prevent rocking of elongated support 27a about
the
pivot assembly 43. The stabilizing roller assemblies at each end of elongated
support 27a are identical and are generally indicated at 47 and 48 in Figures
6 and
8. Figure 10 illustrates the stabilizing roller assembly 47. Since the
stabilizing
roller assemblies 47 and 48 are identical, a description of one will suffice
for both.
A stabilizing roller 48 is rotatively mounted on a shaft 49 and may be
provided
with appropriate bearing means (not shown). The shaft 49 is affixed to
appropriate supports 50 and 51 which depend downwardly from the upper portion
of elongated support 27a. It will be understood that the supports 50 and S1
could
extend from side-to-side of elongated support 27a. At the position of roller
48,
the second elongated support 42 has a support pad 52 welded or otherwise
appropriately affixed to its upper surface, at the transverse center thereof.
The
support pad 52 and support roller 48 are so positioned and sized that the
bottom
edges of the downwardly depending side walls of elongated support 27a are
essentially parallel to the top surface of the second elongated support 42. As
indicated above, the support roller assembly 48 is identical to that described
with
respect to Figure 10. Engagement of the support pads of the support roller
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assemblies :~7 and 48 by the side walls of elongated support 27a will limit
the
amount of pivoting of elongated support ~7a with respect to the elongated
support 42.
w'hzre tracking problems are encountered with respect to the lower return
t~iVht 8b of conveyor belt 8, due to inconsistencies between segments of the
belt.
or for other reasons well known in the art, the use of a return roller
assembly of
the type described with respect to Figures 6-10 may well be advantageous.
Referring to Figure 6. if the return flight 8b, moving in the direction of
arrow B,
tends to shift to the right as viewed in Figure 6, the right end of elongated
support
.7a will tend to pivot forwardly in the direction of arrow B. This, in turn,
will
cause the conveyor belt lower flight 8b to begin to shift to the left as
viewed in
Figure 6. If the lower flight 8b tends to shift too far to the left, then the
left end
of elongated support 27a will pivot forwardly in the direction of arrow B,
tending
to cause the lower flight 8b to shift to the right. This lower flight tracking
correction is automatic and requires very little pivoting of the elongated
support
?7a. In a non-limiting example, the support roller 48 may be capable of moving
about 1/4 inch in either direction from the center of support pad 52, for a
total
movement range of about 1/2 inch.
Herein and in the claims. terms such as "vertical" and "horizontal" are
~0 used in conjunction with the drawings for purposes of clarity. It is to be
understood by one skilled in the art that while the frame of the conveyor will
preferably be maintained transversely horizontal by the use of legs of
appropriate
length, the frame may slope upwardly or downwardly in a longitudinal
direction.
Modifications may be made in the invention without departing from the
spirit of it. For example, it would be possible to substitute a single roller
having
an appropriately crowned profile for the rollers 30, 34 and 35 although the
use of
rollers 30, 34 and 35 is preferred.
