Note: Descriptions are shown in the official language in which they were submitted.
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A TUBULAR BE:LT CONVEYOR
BACKGROUND OF TilE INVENTION
The present invention relates to a tubular belt conveyor
and more particularly to a tubular belt conveyor which comprises
a bel-t guiding device for preventing a belt from loosening or
expanding so as to assure smooth running.
There is a conventional tubular belt conveyor in which an
endless band-shaped conveyor belt is rolled up into a tubular
shape, flattened portions at the front and rear ends are wound
around a front and a rear end roller to convey material which
is thrown onto the front end of a forward belt from a hopper
and is discharged onto a receiver at the rear end.
The portion between a flat and a tubular portion or
between a tubular and a flat portion is called "a trough convert-
ing portion", and the distance therebetween is called "a trough
converting distance".
In the conventional tubular belt conveyor, nylon or steel
is employed as core material for the endless conveyor belt. The
core material made of nylon is liable to lengthen and the trough
converting distance is small, while what is made of steel is
difficult to lengthen and the trough converting distance is large,
as shown in a dotted line.
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A triangle represents the relationship between the elong-
ation and the trough converting dist:ance for an endless conveyor
belt made of different material. The center line and both the
side ends of the conveyor belt are corresponding to the base and the
hypotenuse of the triangle respectively. That is to say, the
hypotenuse is longer than the base, which means that the side ends
of the belt are stretched longer than the center line.
Generally, the trough converting distance of the endless
conveyor belt is determined to keep the elongation less than 1%.
The elongation less than 1% is within elasticity, and when the
belt is formed into a tubular shape, the tubular belt becomes to
have the same elongation over the whole width. In the endless
steel-core conveyor belt the trough converting distance lengthens
so that the difference between the hypotenuse and the base becomes
smaller.
If the trough converting distance lengthens, the trough
converting portion at the beginning part of the return belt
loosens by its weight, and the loosened portion increases because
of the frictional resistance to which it is subject when it runs
through a belt shape maintaining frame. Therefore, when the
endless conveyor belt is driven, said loosened trough converting
portion moves up and down to cause surging action, so that the
conveyor belt travels intermittently. In other words, the running
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speed of the conveyor belt is not constant and the intermittent
shock occurs in the belt, so that it is subject to large tension.
Therefore, the front and rear end rollers around which the
conveyor belt is wound undergo strong force.
Also, if the conveyed material supplied from the hopper
is loaded ununiformly on the forward belt at the trough convert-
ing portion of the beginning part, the forward belt totally
twists, or the side end of the belt expands over the usual
tubular form because of the weight of the conveyed material, so
that the elongation of the side ends of the belt increases,
and the load of the belt and the weight of the conveyed material
make the belt loosened, which results in the problems as
mentioned above.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to
provide a tubular belt conveyor comprising a belt guiding
device to prevent a belt from loosening or expanding at a
trough converting portion so as to assure smooth running.
According to the present invention, there is provided
a tubular belt conveyor comprising a front end roller provided
at the front end of the conveyor, a rear end roller provided at
the rear end, an endless belt which is rolled up into a tubular
shape for conveying material, flat portions of the belt being
wound around the front and rear end rollers so that the belt may
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circulate between the two end rollers and a belt
guiding device disposed at the portion in which the
belt is rolled up from a flat shape into a tubular
shape, the device comprising a base plate and a
plurality of guide frames provided on said base plate
the guide frame having a plurality of guide rollers
arranged like a circle through which the belt to be
rolled up passes, the improvement comprising that the
diameter of the circle formed by the guide rollers
within the guide frame increases gradually towards the
front or the rear end roller.
Therefore, even if the belt is twisted around its
longitudinal axis or expanded to open by the weight of
the conveyed material or itself, it can be guided
smoothly in a circular or an arcuate form such that its
diameter increases or decreases gradually. When
twisted, the belt only moves within the inscribed
circle of each guide frame, but no adverse effect can
be created during running.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects as well as advantages of
the present invention will become clear by the
following description of a preferred embodiment of the
present invention with reference to the accompanying
drawings, wherein:
Fig. 1 is a schematic side view of a tubular belt
conveyor according to the present invention in which a
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belt guiding device is provided at the beginning part
of a return belt;
Fig. 2 is a vertical sectional view taken along
line A-A in Fig. l;
Fig. 3 is an enlarged plan view of the
terminating end of the forward belt in the tubular belt
conveyor shown in Fig. l;
Fig. 4 is a side elevational view taken in the
direction of the arrows B-B in Fig. 3;
Fig. 5 is an enlarged sectional view taken along
line C-C in Fig. 4;
Fig. 6 is an enlarged sectional view taken along
line D-D in Fig. 4;
Fig. 7 is an enlarged sectional view taken along
line E-E in Fig. 4;
Fig. 8 is a sectional view showing another
embodiment of a conveyor belt to which the present
invention applies;
Fig. 9 is a sectional view showing further
embodiment of a conveyor belt to which the present
invention applies;
Fig. 10 is a schematic side view of a
conventional tubular belt conveyor and similar to Fig.
l;
Fig. 11 is a view showing the relationship
between elongation and trough converting distance for
different core material, when an endless conveyor belt
is employed for a tubular belt conveyor; and
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Fig. 12 is a side view similar to Fig. 4 and
illustrates the conventional tubular belt conveyor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The embodiments according to the present
invention will be described in detail with reference to
Figs. 1 to 9 in appended drawings. To the parts common
with those in the prior arts illustrated in Figs. 10 to
12, the same numerals will be given.
Fig. 1 schematically shows a tubular belt
conveyor according to the present invention in which a
belt guiding device is provided at the beginning part
of a return path of an endless conveyor belt. An
endless conveyor belt 1, the flattened front and rear
end of which are wound around a front end roller 2 and
a rear end roller 3 respectively, is circulated in a
direction shown by an arrow by means of drive means~not
shown).
A plurality of belt shape maintaining frames 6
are provided between two end rollers 2 and 3. Between
a front end belt shape maintaining frame 6 and a
flattened part at the beginning end, namely, a trough
converting portion, a belt guiding device 7 is
disposed. The numerals la and lb represent a forward
and a return path respectively.
As shown in Fig. 2, each belt shape maintaining
frame 6 is divided into an upper compartment 6b and a
lower compartment 6c each of which includes in the
center an opening 6a through which the conveyor belt 1
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passes. Within each compartment 6b and 6c, a plurality
of belt shape maintaining rollers 8 are arranged like a
circle around the opening 6a. The numeral 9 represents
conveyed material.
As shown in Figs. 3 and 4, the return path lb
running around the front end roller 2 is supported by
the belt guiding device 7 at the trough converting
portion adjacent to the first belt shape maintaining
frame 6. The belt guiding device 7 comprises a base
plate 70 which is located below the return path along
its moving direction to support a first, a second and a
third hexagonal guide frame 71, 72 and 73.
As shown in Fig. 5, the first hexagonal guide
frame 71 includes in the center a circular opening 71a
through which the conveyor belt 1 passes, and six guide
rollers 10 are arranged like a circle inside the
opening 71a. These guide rollers 10 engage with the
circumference of the belt 1 to guide it.
As shown in Figs. 6 and 7, the second and third
hexagonal guide frames 72 and 73 are similar to the
first hexagonal guide frame 71 in structure, as
mentioned above. The three frames are analogous and
become smaller in order. Especially, it should be
noted that the diameters 71a, 72b and 73b of inscribed
circles formed by connecting the outer peripheries of
the guide rollers 10 becomes smaller gradually.
This belt guiding device 7 may be used in
combination with lobe-shaped rollers (not shown) which
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support the return belt of the trough converting
portion lc.
In Fig. 1, the numeral 11 shows a flow-down tube
which is integrally connected with the hopper 4.
The function which is performed by the invention
in the above-mentioned embodiment will be described
hereafter. Fluidizable powdered material 9 in the
hopper 4 flows down through the flow-down tube 11 onto
the forward path la, which runs through each belt shape
maintaining frame 6. The forward path la which gets
out of the belt shape maintaining frame provided at the
upper end opens, so that the conveyed material 9 is
thrown onto a receiver 5 surrounding the front end
roller 2.
The return path lb travelling around the front
end roller 2 is subject to frictional resistance when
it enters into the belt shape maintaining frame 6
provided at the front end. Thus, the trough converting
portion becomes slackened. But, the slackness can be
decreased by the guide frames 71, 72 and 73 so as to
guide the return path lb into the upper belt shape
maintaining frame 6 smoothly, and, then, this return
path lb passes through the lower compartment 6c in each
belt shape maintaining frame 6 to come back to the rear
end roller 3 for circulation.
The embodiment mentioned above relates to a
tubular belt conveyor in which a flattened belt is
rolled up into a tubular shape by overlapping the inner
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surface of one side end on the outer surface of the
other side end along its entire length, but the present
invention may also apply to a tubular belt conveyor in
which a flattened belt is rolled up by contacting the
inner surfaces of both side ends with each other to
form a projection as shown in Fig. 8, or by contacting
or approaching the side edges to each other along its
entire length.
Also, as shown in Fig. 9, the present invention
may apply to further embodiment of a tubular belt
conveyor in which a conveyor belt 81 is supported by a
plurality of belt shape maintaining rollers 82. Three
upper rollers 82 and three lower rollers 82 are
connected by an upper and a lower link 83 and 84
respectively. The links 83 and 84 are supported at the
side ends by a U-shaped support frame 85. The belt
guiding device in the present invention can prevent a
belt from loosening so as to assure smooth running. In
such a conveyor, the forward and return paths are
arranged side by side horizontally, which is different
from a vertical arrangement in the foregoing
embodiments.
Further, the embodiment mentioned above describes
a belt guiding device provided on the trough converting
portion at the beginning part of the return belt to
prevent the belt from loosening. However, the device
may be provided at the beginning part of the forward
belt. In this case, it not only prevents the belt from
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loosening which is caused by the weight of the conveyed
material, but also the belt can be smoothly guided as a
tubular or arcuated shape even if the belt is twisted
or is loaded to open the side edge of the belt.
Also, the belt guiding device may be provided at
the terminating end of the forward or the return path,
whereby the belt may be guided smoothly as well.
In each guide frame 71, 72 and 73 of the
above-mentioned embodiments, the guide rollers 10 are
arranged like a hexagon, but may be like other
polygons.
The belt guiding device according to the present
invention may be located at any trough converting
portion of the beginning and the terminating parts of
the forward or the return path of the belt. By the
location, the belt can be smoothly guided in a tubular
or an arcuate form without disadvantages such as
loosening or spreading of the opening, even if the belt
is twisted around its longitudinal axis or is
undesirably loaded by the weight of conveyed material
or belt itself. Therefore, it is advantageous to
prevent the belt from surging at the trough converting
portion so that it may always run at constant speed and
not to give the belt large stress which effects impact
to members such as the front or the rear end roller.
It should be noted that the foregoing only
relates a preferred embodiment of the present
invention, and that modification or variation may be
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made by person skilled in the art without departing
from the spirit of the invention.
The scope of the invention is therefore to be
determined solely by the appended claims:
