Conveyors: power-driven – Conveyor section – Screw
Patent
1995-12-06
1998-03-03
Bidwell, James R.
Conveyors: power-driven
Conveyor section
Screw
198670, B65G 3300
Patent
active
057225290
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a discharge device which works as a feeder for uniform discharge of bulk solids from silos and stockpiles. The device is also designed to work as a homogenizer and a continuous mixer. Due to the versatility of this device with regards to reclaiming solids, it is named "The Universal Feeder".
2. State of the Prior Art
Bulk materials in particulate form such as lumps, granules and powders are an important class of raw materials in the process industry. Handling large quantities of particulate materials requires them to be stored, discharged, and transported to, and often from processing operations.
Such handling operations can affect the quality of the material. There exist a large number of unresolved problems in both ensuring satisfactory filling procedures and complete emptying of silos, as well as ensuring that the material that is discharged has an even quality.
Bulk materials are usually stored in silos and there are many devices to promote the flow of solids in silos and to ensure their discharge. Some of them give rise to mass flow, while others simply promote nearly total discharge. Industry would ideally like to use silos with a high degree of volume utilization. This is realized in the flat bottomed silos.
The most commonly used discharge device for this purpose is the screw feeder. The screw rotates about its own axis, and also sweeps across the entire bottom of the silo. The feeder is thus exposed to the head of solids stored in the silo. There are disadvantages with this device with regard to uniform discharge and high energy consumption. With regard to the consumption of energy in case of flat bottomed silo configurations, it is about 70% more than a tubefeeder. There are also many instances wherein the screw reclaiming in a flat bottomed silo has failed. This is due to a very high torque requirement.
From U.S. Pat. No. 4,351,627, we are aware of a feeding device for discharging bulk solids from silos. This feeder is basically a screw conveyor located inside a tube which has slots. The two units rotate in opposite directions, and the bulk solids feed into the slots uniformly along the tube. The screw conveyor normally rotates faster than the tube. The tube protects the screw which takes care of the horizontal transportation.
high manufacturing costs, and
high installation costs.
even quality of the feed,
mass flow in silo, and
controlled segregation
A second Swedish patent application, No. 8902138, describes a variable geometry bulk material mixer and feeder. This consists of a tube feeder of the type described previously. It is used in conjunction with long slotted plane flow silos. The silo has partitions and hence can be used to store at least two types of powders. The feasibility of the system was, however, not investigated. Hence, it is difficult to comment on the quality of this device. However, it can be thought that the advantages and disadvantages as previously mentioned hold true in this case as well.
SUMMARY OF THE INVENTION
The object of the invention is to obtain a device for even draw-down of bulk materials stored in plane flow or flat bottomed silos or stockpiles. While being discharged the material should not be crushed or degraded. Another object is to produce a device which can be very energy efficient, relatively simple to construct and cost effective.
The above and other objects of the invention are obtained with a device as described below.
The invention concerns a discharge device having inner and outer tubes with inlet openings/slots for the feed of solids from the silo and an outlet for the same. The inlet openings are distributed over the periphery and along the length of the tube. The inner tube is provided with a helical screw flight attached to its inside. It is rotatable about a longitudinal axis. The screw flight may have a central shaft. The telescopic outer tube with slots can be used to vary the slot size as required by rotating the inner tube. While discharging bulk soli
REFERENCES:
patent: 1050171 (1913-01-01), Riblet
patent: 4266902 (1981-05-01), Forsberg
patent: 4351627 (1982-09-01), Forsberg
patent: 4393609 (1983-07-01), Persson
patent: 4493442 (1985-01-01), Hanson, Jr.
patent: 4511066 (1985-04-01), Forsberg
Manjunath Konanur Srikantiah
Roberts Alan William
Bidwell James R.
Norsk Hydro a.s.
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