Conveyors: power-driven – Conveyor system having a gravity conveyor section – Condition responsive
Reexamination Certificate
1999-08-12
2001-03-13
Ellis, Christopher P. (Department: 3651)
Conveyors: power-driven
Conveyor system having a gravity conveyor section
Condition responsive
C198S532000, C414S143100, C141S264000
Reexamination Certificate
active
06199684
ABSTRACT:
THIS INVENTION relates to bulk materials handling. In particular, the invention is directed to apparatus for delivering bulk materials in a controlled manner. The invention has particular application to the loading of coal, grain or other particulate or powdered material onto ships, although the invention is not limited to those particular uses.
BACKGROUND ART
When loading bulk material, such as coal or grain, into the hold of a ship, the bulk material is normally carried by a belt conveyor to a position above the hold to be filled, and then discharged under gravity into the hold. There are several problems associated with this basic loading method. First, the falling material generates a considerable amount of dust, posing health risks and fouling the environment. The fall from the conveyor into the hold is also likely to degrade the product, and cause unwanted aeration. The impact of the material on parts of the ship or other equipment accelerates abrasive wear of such parts of equipment.
Various types of bulk materials handling equipment have been developed in order to reduce one or more of the abovementioned problems. One device, sold under the trade name CHOKEFEEDER, attempts to minimise dust generation during loading by discharging the product into a spout at the end of the belt conveyor, and “choking” off or sealing the bottom of the spout by a set of vanes which are either fully opened or closed. Material is fed continuously into the top of the spout and freefalls down the spout. When the product builds up to a predetermined height, the vanes are opened fully to discharge the product. When the product level in the spout falls to a level near the bottom, the vanes are closed until the product builds up to the upper limit again.
Although this device reduces dust generation, it still allows the product to free fall, on average, an appreciable distance (which can be up to the full height of the spout). The product gains speed and tends to segregate while free-falling. Its movement is then halted abruptly as it impacts against the stationary product at the base before being forced through the discharge control valves. The operation involves repeated filling and emptying of the spout.
The upper and lower product operating heights of the CHOKEFEEDER can be varied for different products. When loading fragile materials, such as petroleum coke, the control system varies the discharge vane opening and closing times to keep the working range of the product closer to the upper end of the spout to limit the distance that the product falls. Since the vanes are either fully open or fully shut, the product is still subjected to the repetitive starting and stopping motion which results in product degradation and some dust generation. Further, as the vanes open and close frequently under load, large inertia forces are generated as the column of material stops and starts suddenly.
Another known method of material transfer uses a series of hoppers or cones. Material cascades from one cone to the next down the length of the feeder. The design tries to limit the maximum velocity achieved by the material in the spout. However, this method still results in the product accelerating and decelerating from one cone to the next.
It is an object of the present invention to provide an improved materials handling system which overcomes or ameliorates at least some of the abovedescribed problems, or which at least provides a useful alternative.
SUMMARY OF THE INVENTION
In one broad form, this invention provides apparatus for loading bulk material, comprising
a conduit having an inlet at its upper end adapted to receive a flow of the material, and having a discharge outlet at its lower end,
a controllable gate mechanism at the lower end of the conduit for regulating the flow of material through the outlet,
means for sensing the level of material in the conduit, and
control means having an input connected to the level sensing means and adapted to control the operation of the gate mechanism to maintain the conduit substantially or nearly full of material during steady state operation, wherein the gate mechanism is able to be fractionally or partially opened by the control means.
In another form, the present invention provides a method of bulk materials handling in which material flows into an inlet at the top end of a conduit and is discharged through a controllable gate mechanism having a fractionally variable opening at the bottom end of the conduit, the method comprising the steps of
sensing the level of material in the conduit, and controlling the operation of the gate mechanism so that the conduit is kept substantially or nearly full.
Typically, the materials handling system is used for loading particulate product. The product, which may be conveyed to the loading site by a belt conveyor, is loaded into a receptacle, such as a ship's hold, through the conduit. At start-up, the gate mechanism is closed or only partly opened until the conduit is full or nearly full. Thereafter, during steady state operations, the gate mechanism is controlled to permit discharge of material from the conduit at a rate matching the infeed rate, thereby maintaining a full column of material in the conduit. That is, the gate mechanism is not necessarily fully opened, but rather its opening is proportionately or fractionally controlled. The material is therefore “extruded” through approximately the full height of the conduit in a fully controlled motion with near constant velocity, rather than free-falling into a pile.
Preferably, the system also includes means for monitoring the flow of material into the conduit. If the material is delivered to the conduit by a belt conveyor, such means may suitably be in the form of a belt weigher the output of which is fed to the control means. The conduit can therefore be “preconditioned” to accommodate variations in material infeed rate.
The conduit may be of fixed length, or may be of variable length, e.g. telescoping. The gate mechanism can be regulated by the control means to accommodate changes in the length of the conduit.
Preferably, a variable speed conveyor belt is located immediately below the bottom end of the conduit, the speed of the belt being controlled by the control means. By controlling the gate mechanism and regulating the speed of the discharge belt conveyor, the control means is able to accurately control the rate of material discharge from the conduit.
Typically, the control means is a programmable controller.
In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawing.
REFERENCES:
patent: 1448272 (1923-03-01), Kelly
patent: 1852385 (1932-04-01), Weigert
patent: 3526344 (1970-09-01), Koning
patent: 3858733 (1975-01-01), Morioka et al.
patent: 4225033 (1980-09-01), Fukagai et al.
patent: 4270671 (1981-06-01), Arnold
patent: 4658992 (1987-04-01), Peleus
patent: 5016686 (1991-05-01), Gerstenkorn
patent: 5697408 (1997-12-01), Reeves
Deuble Mark A
Ellis Christopher P.
Gladstone Port Authority
Wells, St. John, Roberts Gregory & Matkin P.S.
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