Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BACKGROUND OF TME INVENTION
It is well known to elevate or lower bulk ma'cerials7 ~;
including granular materials, betwéen various levels by belt
conveyors which face one another.
In some of these conveying apparatus, compressible
foam, varying in compressibility from the side to the middle,
is used, so as to provide edge-to-edge belt contact with the
central portion of the belts in engagement with the material.
While this arrangement may be satisfactory for discrete package
handling, it has not been found satisfactory for handling
granular material such as crushed rock or coal because of the
fines present.
In order to overcome the problems ~ust enumerated,
the use of fluid pressure applied to the rear of the belts in : :
the elevating section has been suggested, see recently issued
U.S. patent No. 3,762,534. An improved conveyor wherein higher
fluid pressures are applied to the edges ~than to other parts
of the belts) to maintain the edges in contact with one another
is described and claimed in U.S. patent 3,948,383. ` :
In French patent No. 1,123,345, edge rollers are
provided to keep the edges of the beits in contact to substan-
tially eliminate spillage and leakage.
SUMMARY OF THE INVENTION
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According to this invention, there is provided in a
bulk handling apparatus, especially adaptable to transport a
variable volume of granular material between various levels, a
pair of flexible, endless belts having a change of elevation ~ . -
section in which the belts are in face-to-face relationship -:~ '
presenting flat belt edges in engagement with one another~ The .
belts are moved at the same speed by suitable drive means~
Mechanical means engage the respective edges of the belts in
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the change of elevation zone to maintain the belt edges in ~ ;~
abutting relationship and to thereby substantially eliminate
spillage of material being transported from between the belts.
The mechanical means include sets of edge rollers of predeter-
mined diameter at each side of the belts which engage the
edges of the belts in the change of elevation zone and serve as
substantially the sole positioning and supporting means for the
belts in the elevation zone. The rollers are staggered in
respect to one another and positioned to cause the edges of the
belts to follow a sinuous path as they pass between the
rollers. The axes of the sets of rollers define juxtaposed
planes oriented in the same face-to-face relationship as the
associated belts. Each of the rollers have a smooth
cylindrical peripheral surface in engagement with the flat edge
of the confronting belt permitting the latter to move relative
to the peripheral surface in laterally inward and outward
directions as the cross-section of the material conveyed
between the belts increases and decreases r respectively. The
edge rollers of one set are spaced vertically at intervals in
the range of 2 to 5 times the diameter of one of the edge
rollers. The parts of the belts between the edges engaged by
said edge rollers travel in a smooth path in the elevation zoné ;~
whereby the granular material is conveyed en masse in substan-
tially column form in the elevation zone.
The axes of the sets of edge rollers may define ;-
planes spaced from one another a distance not greater than the
sum of the thickness of the two belts less .05 times the
spacing interval of the edge rollers~ The edge rollers may
have equal diameters and both sets of rollers may be spaced at
equal intervals.
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DESCRIPTION OF T~E DRAWINGS
Fig. 1 is a side elevation of a bulk material
handling apparatus constructed according to this invention;
Fig. 2 is a sectional view taken on line II-II of
Fig. l; and
Fig. 3 is an enlarged view of the staggexed edge
rollers of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates an apparatus for elevating bulk
material, especially granular bulk material, wbich comprises a
pair of endless, flexible belts 10 and 12 which have parts in ~;
face-to-face relationship in a change of elevation section
between pulleys 28 and 30. The belt 10 is entrained over
pulleys 14, 16, 18, and 20, the pulleys 14 and 16 being spaced
from each other at the lower level and generally horizontally ;
positioned, while the pulleys 18 and 20 are generally
horizontally positioned and spaced from each other at the upper
level. One or more of these pulleys may be driving pulleys.
As illustrated the belt 10 has a substantially C-shaped con-
figuration forming a substantially horizontal loading section
22 to receive bulk material from a chute 24 or similar device,
a vertical elevating portion 25, and an upper portion which is
angularly disposed to form a discharge section 26.
The belt 12 is entrained over pulleys 28, 30, 32 and
34, one or more of which may be driving pulleys. In any event,
the belts 10 and 12 are driven at the same speed. The pulleys
28 and 30 are large pulleys which deflect the elevating portion
27 of the belt 12 into engagement with the elevating ~portion 25
of belt 10. The pulleys 30 and 32 are horizontally spaced from
3~ one another so that a bèlt discharge section 26 is Eormed and
the pulley 34 is a snub pulley to maintain the belt 12 taut.
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The belts 10 and 12 cooperatively engage one another
between lower pulley 28 and upper pulley 30 to provide a change
of elevation zone. In order to substantially eliminate spill-
age and leakage from the edges of the bel1:s, there is provided
a plurality of edge rollers 46, 47 which engage the edges of
the belts in order to effectively maintain them in engagement
with one another. As shown in Figs. 1 and 2, the rollers 46
are mounted for rotation on shafts 48 supported in brackets on
vertical supports 50, 52. Likewise, shafts 49 for rollers 47
are mounted on brackets secured to vertical supports 54, 56.
Inasmuch as the belts are driven, no power is generally
required for the edge rollers 46, 47; however, if desired, the
edge rollers 46, 47 can be power driven without departing from
the spirit of the invention.
As illustrated in Fig. 3, the axes 71 are spaced a
distance S from one another and the axes 72 are spaced the same
distance S from one another. The edge rollers 46, 47 rotate on
axes 71, 72 lying in two parallel vertical planes spaced a
distance e from one another. The juxtaposed planes defined by
the axes 71, 72, respectively, are oriented in the same face-
to-face relationship as the associated belts lO, 12. That is,
as viewed in the drawings, the plane through axes 71 is to the
left of the plane through the axes 72, just as the belt lO
associated with rollers 46 i5 to the left of the belt 12
associated with rollers 47. The rollers 46, 47 are so
positioned as to force the belt edges to stretch and follow a
sinuous path between the two sets of rollers 46, 47. In
Fig. 3, the sinuous path of the belt edges is evident. As the
belts travel upwardly together between the rollers 46, 47, the
belt edges are alternately displaced laterally (in relation to
the direction of the belt) from one side to the other. The ~ ~`
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deflection of the belt edge by one roller 46 acting on the belt
10 in opposition to the two nearest staggered rollers 47 causes
the edge of the belt 10 to assume a curve as predicted by the
elastic beam theory. The portion 62 of the edge of the belt
12, because of its position on the outside of the curve, must
assume a curve of greater radius than the confronting edge
portion of belt 10 thereby stretching its edge. This produces ~
a localized tension in portion 62 forcing it into sealing ;~ ;
contact with the confronting edge o~ belt 10. The local
tensions in the belt edges alternate from belt~to~belt as the
belt edges pass between the rollers and effectively keep the
belt edges in sealing engagement with sufficient force to
virtually eliminate edge spillage of material being conveyed
from one level to another. Although the staygered rollers 46, ~ ;
47 cause the belt edges to follow a zigzag course, the column
of conveyed material compressed by the belts is relatively
stiff and will not zigzag but rather it will remain in column
form and it, and the intermediate parts of the belts acting
against the column, will move in a smooth path.
As the cross-section of material being conveyed
changes, the central portions 66, 68 will bow or belly out more
or less as the material cross-section requires. The changes in
cross-section of material being elevated will cause the edges
of the belts to move laterally in or out on the edge rollers.
It will be noted that the edge rollers have smooth cylindrical
rolling surfaces, thus readily permitting the belts to move
laterally in-and-out as the elevated material cross-section ;
changes. Accordingly, the cylindrical edge rollers and flat
belt edges permit the dual belt elevator ~o convey a variable
volume of bulk material.
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In carrying out my invention, I prefer certain para-
meters for size and relationship of various components ~or ;~
instance, I prefer to establish the distance e in inches
between the two planes defined by the axes 71, 72,
respectively, by the following formula:
e = tl ~ t2 - (.10 ~ .05) S
Wherein; tl is the thickness in inches of belt 10, t2 is ~he
thickness in inches of belt 12 and S is the distance in
inches between the axes of adjacent edge rollers at the
back side of one of the belts 10, 12.
Preferrably tl equals t2 and the spacing of rollers 46 is the
same as the spacing of rollers 47. For most applications I
believe e ~ tl + t2 ~ .05S to be a satisfactory maximum
spacing. The spacing S between rollers will be at least equal
to the diameter d of the rollers. The maximum spacing S in
inches may be expressed by the formula:
S = 160 u d ;~
v F w `
Wherein: u is the coefficient of friction between the bulk
material being conveyed and the belt, d is the diameter of
the edge roller in inches, v is the density of the
material being conveyed in pounds per s~uare foot, F is
the free width of the belt in inches (the width of the
belt disposed between the laterally inner ends of the edge
rollers) and w is a lump size constant for the bulk
material being conveyed which varies from about .07 for -
lumpy material to about .2 for fine material.
I believe that for most applications the spacing
interval S of 2 to 5 times the diameter d of the rollers will ~-
provide satisfactory results. A satisfactory belt elevator for
handling bulk material can be provided by using edge rollers
which are 2.5 inches in diameter, 3 inches in length and are
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spaced on axes 6 inches apart and by spacing the axes of the
two series of edge rollers so as to define planes 2 inches ~;
apart.
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