Field of the Invention
This invention relates to a device to collect by an air flow powder
material displaced from its allocated passage on a belt conveyor, separate the
collected material from the air flow, and return it onto the belt conveyor or place
it onto another belt conveyor.
Conventionally, providing seal members or skirts beside the lower
end portion of a chute disposed above a belt conveyor is well-known to prevent
powder material from escaping from the powder material conveying system. However,
since the powder material fed from the chute and the air in the chute pressurized
by the powder material are imparted great energy, the powder material tends to
be blown from under the skirt and dropped from the belt conveyor. The blown powder
material must be manually removed or placed again onto the belt conveyor.
In order to avoid this, another known device (DD 132 481 A2) provides
a duct device disposed adjacent and outside the lower ends of the chute and above
the belt conveyor for collecting said displaced material by suction (vacuum cleaning)
and decreasing the pressure difference between the inside and outside of the chute
walls at the discharge opening.
Japanese Utility Model Laying-Open (Kokai) No. 63-136,747 teaches
a device to separate powder material from an air flow. The device has a hollow
horizontal cylinder, or a centrifugal separator chamber, which has an intake at
one end to receive an air flow and powder material entrained therewith, and an
air outlet at the other end, and which has an elongated gate axially formed in
the bottom to centrifugally separate the powder material from the air flow. The
air flow entering the intake, together with the powder material, passes along the
inner surface of the cylinder. The powder material is thrown through the gate
by centrifugal force. Thus the powder material is separated from the air flow.
If the density of the powder material in the air flow is high and thus the powder
material is oversupplied to the centrifugal separator chamber, that powder that
cannot be separated at the gate tends to fill the space around the air outlet
nozzle and is then fed out of the air outlet into the air discharge system. A receiving
chamber is disposed below the gate to receive the separated powder material. However,
it is difficult to make the receiving chamber air-tight because of the need to
remove the collected material therefrom. If suction is used as a source of air
flow, an air flow from the receiving chamber tends to pass the gate and enter the
cylinder to hinder the revolution of the powder material in the centrifugal separator
chamber, resulting in the accumulation of the powder material therein. If the accumulation
grows to a certain extent, the powder material not only tends to be carried out
of the air outlet, but also to hinder the air flow in the centrifugal separator
chamber and to decrease the rate of air flow, resulting in remarkably lowering
the efficiency of the centrifugal separation, which is very disadvantageous.
Summary of the Invention
This invention as defined in claim 1 and its dependent claims aims
to resolve the drawbacks mentioned above and to provide a device to automatically
carry, by an air flow, powder material that leaves the allocated passage on a belt
conveyor and separate the powder material from the air flow and return it on the
same belt conveyor or place it onto another belt conveyor. In this invention, "powder
material" includes granular or particulate material that can be carried by an air
The device of the invention automatically collects the powder material
by an air flow and separates it from the air flow and dumps it onto the same or
another belt conveyor. When the blower is driven, an air flow is generated in the
duct device. The air flow carries powder material from the duct device into the
cylinder. Since the air flow passes along the inner surface of the cylinder, the
powder material is thrown through the slit by centrifugal force, thereby accumulating
in the chamber. When the weight of the accumulated powder material reaches a certain
point which corresponds to the weight of the weighted damper, the damper automatically
opens, thereby dumping the accumulated powder material onto a conveyor belt.
Brief Description of the Drawings
Fig. 1 is a schematic side view of an embodiment of the automatic
device of the invention.
Fig. 2 is a cross section along line II - II in Fig. 1, shoeing a
sectional view of a duct device disposed adjacent a chute and a belt conveyor.
Fig. 3 is a perspective view of the duct device with the chute and
belt conveyor of Figs. 1 and 2, wherein the duct device and chute are cut into
halves, and the halves are separated to show their insides.
Fig. 4 is a perspective view of the powder material separating device
of the automatic device of Fig. 1.
Fig. 5 is a cross-sectional side view taken along line V - V in Fig.
Fig. 6 is a cross-sectional front view taken along line VI - VI in
Detailed Description of the Preferred Embodiment
In Fig. 1 an upper belt conveyor 1, a lower belt conveyor 2, and a
chute 3, are arranged so that powder material is transferred from the upper belt
conveyor 1 onto the lower one through the chute 3. The chute 3 is confined by walls,
except that its bottom is open and faces the lower belt conveyor 2. A part of its
rear wall is also open to receive the downstream end of the upper belt conveyor
1. Its top wall is provided with an opening to communicate with a dust collector
(not shown). The lower belt conveyor 2 is greater in width than that of the chute
3, which is positioned in the middle of the conveyor, leaving room for spaces on
both sides of the chute 3.
A duct device 10 is disposed on both sides of the lower part of the
chute 3 and above those parts of a conveyor belt 4 of the lower conveyor 2 that
are not covered by the chute 3. As shown in Figs. 2 and 3, the duct device 10 has
two ducts 16, one disposed on each side of the chute 3. Each duct 16 has an inner
wall 15 and an outer wall 17, thereby defining therebetween a passage for powder
material on the conveyor belt 4. The tops of the inner and outer walls 15, 17 are
bent so as to form a top for each duct. The inner wall 15 extends horizontally
farther than the outer wall 17, as shown in Figs. 1 and 3. A rubber skirt, or seal
member 15A, is attached to the lower end of the inner wall 15, which is spaced
apart from the conveyor belt 4. The rubber seal member 15A contacts the conveyor
belt 4 to minimize the amount of powder material 9 that leaks from under the seal
member 15A. The powder material 9 that passes the lower end of the seal member
15A enters a space 18 defined by the inner and outer walls and conveyor belt 4.
Each duct 16 has an opening 19A at its upstream end for air intake. The outer wall
17 of each duct has a slit, or opening 19, (see Fig. 2) at its lower part adjacent
the conveyor belt 4. The slit may be formed by cutting the lower end of the outer
wall so as to leave a space between the wall and the conveyor belt 4. This slit
acts as an air intake. These ducts 16, 16 are connected by a convergent duct part
11 that straddles the powder material passage on the conveyor belt 4. The duct
part 11 has an outlet 12. This outlet 12 is connected to a suction pipe 13 which
is in turn connected to an intake 33 of a powder material separating device 30
disposed downstream and above the belt conveyor 2.
An additional duct device 10A, which is shown in broken lines in Fig.
1 and which is similar to the duct device 10, may be provided under a return roller
2A. The powder material adhering to the surface of the conveyor belt 4 is scraped
and dropped by the return roller 2A into an opening of a duct positioned below.
The collected powder material is then conveyed by the suction from the blower 40
through a duct that leads to the intake 33.
As shown in Figs. 4, 5, and 6, the separating device 30 has a concentric
outer hollow cylinder 31 and inner hollow cylinder 32. These cylinders 31, 32
extend horizontally and parallel to each other. A part of the side wall of the
outer cylinder is cut open near one of its ends and connected to the intake 33 as
shown in Figs. 4 and 5. The other end of the outer cylinder 31 is closed by a
hollow conical frustum 31A, while the first end, except for the space occupied
by the inner cylinder 32, is closed by a flat annular plate 31B. A slit, or gate
34, is formed in the bottom of the outer cylinder 31, over the length of the cylindrical
part thereof. One end of the inner cylinder 32 protrudes outwardly beyond the plate
31B forming the first end of the outer cylinder 31 and is connected to an intake
port 41 of a low-pressure blower 40, which has an outlet port 42. The other end
of the inner cylinder 32 is spaced apart from the conical frustum 31A of the outer
cylinder 31, thereby providing a space 39 therebetween.
A hopper, or chamber 35, is disposed below the outer cylinder 31.
The chamber has a bottom 36 that can be opened and closed in any conventional
way. The bottom 36 is preferably a weighted damper having a weight 14 and a hinged
According to the structure of the device to automatically collect
and separate powder material from the air flow, the suction blower 40 is begun
to be driven before powder material is fed onto the belt conveyor 2 through the
chute 3, so that air flows through the openings 19A and 19 into the ducts 16. Thus
the powder material fed onto the conveyor belt 4 and that happened to enter the
air space 18 is carried by the air flow into the outer cylinder 31. The air flow
passes between the outer and inner cylinders with the centrifugal force causing
it to flow, rotating along the inner surface of the outer cylinder, and the powder
material entrained in the air flow is thrown out of the space through the slit
34 into the chamber 35 by centrifugal force. The air then flows into the inner
cylinder 32 and through the blower 40 and is discharged from the outlet 42.
During the process, if an excessive supply of powder material is
introduced into the cylinder 31, and cannot pass through the slit 34, the powder
material is pressed against the inner wall of the conical frustum 31A due to inertia.
Thus the powder material is not brought into the blower 40. Since the space 39
near the conical frustum 31A functions as an area that can reduce the rate of the
air flow, this enhances the effect to prevent the powder material from being brought
into the blower. Further, the configuration of the conical frustum causes the accumulated
powder material to slip down to the chamber 35 through the slit 34 when the operation
of the blower 40 is stopped, thereby preventing the growth of an accumulation of
powder within the cylinders 31, 32.
Further, during the process, since the air pressure in the outer cylinder
31 is negative, i.e., lower than the air pressure outside the cylinder 31, the
weighted damper 36 is tightly closed due to the pressure difference. Thus an air
flow from the chamber 35 to the cylinder 31 does not occur. When the process is
completed and the operation of the blower is stopped, the negative pressure caused
by the suction is relieved, so that due to the weight of the accumulated powder
material the damper rotates about the hinged support to be opened. Thus the material
is automatically discharged onto the conveyor 2. If the sealing property of the
damper is lowered for any reason and an air flow occurs from the chamber 35 through
the slit 34 into the cylinder 31, the air flow might hinder the flow of the powder
material through the slit 34. However, even then since the flow of the powder material
is directed towards the conical frustum 31A, the speed of the revolving movement
of the powder material is maintained, thereby enabling the efficiency of the separation
of the powder material to be maintained.