Conveyors: fluid current – Intake to fluid current conveyor – Movable inlet
Patent
1996-11-25
2000-03-14
Ellis, Christopher P.
Conveyors: fluid current
Intake to fluid current conveyor
Movable inlet
406114, 406134, 406141, 406142, 406143, 406151, 406152, 406153, B65G 5340, B65G 5324, B65G 2314
Patent
active
060364084
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an extraction apparatus for bulk material containers, in particular for bins filled with a pourable material.
In many technical fields, particularly also in the plastics-processing industry--but not only there--the starting products to be processed are in the form of a pourable bulk material. These are often delivered in filled bins, so-called Oktabin containers. A wide variety of emptying and extraction devices have been disclosed for emptying bins of this type with automatic material conveying. In these cases, there is often the problem that, depending on requirements, the bins firstly have to be emptied only partially and have to be stored again in the meantime until the respective bulk material is again required for processing.
Emptying bins of this type regularly takes place using extraction devices.
The most frequently used extraction device comprises a suction tube, also called a suction lance or suction pipe, which preferably comprises two tubes which are pushed one inside the other and, by means of spacers between the inner and the outer tubes, provide an air gap. Via this annular air gap, the conveying air required for pneumatic conveying is also sucked in. The suction tube is usually connected to a flexible conveying hose and is inserted into the bulk material from above. The suction pipe in the form of a double tube is intended to ensure that a specific minimum suction/flow velocity of, for example, 18 m/s for a pourable bulk material is maintained in each case.
In addition to the known methods in which the suction tube is usually inserted into the bulk material from above, methods have also been disclosed, in which the bulk material bins are tapped with the suction tube.
However, multiple problems occur with these methods and apparatuses.
For instance, it is always difficult to set and maintain the correct mixing ratio between air and bulk material for optimum pneumatic conveying. In particular, there is the risk, with a decreasing filling level in the bin, that the suction tube and its opening suddenly rest on the surface of the bulk material and, owing to a lack of material at the intake opening of the suction pipe, the conveying flow is reduced or interrupted.
It is likewise possible for the suction pipe to tilt in connection with the conveying hose and only to suck in air, as a result of which the conveying flow is likewise interrupted.
The suction hose can likewise also become jammed on the edge of the bin, such that the intake opening of the suction tube is no longer able to follow the decreasing filling level.
In the event of an excessive vacuum being generated and, as a consequence thereof, in the event of an excessive suction effect, the suction tube may additionally become blocked.
Finally, it has also been established that, in particular in the case of not readily pourable material, a cavity (void) is formed at the extraction point in the pourable material and, for this reason too, the conveying operation is interrupted owing to a lack of material at the extraction point.
Finally, it is even possible, in particular in the event of high vacuums, for the suction tube to suck through to the base of the bin and there to "choke" on a container film in which the pourable bulk material is generally contained in the bin.
If--as was described and mentioned above--the suction tube is fitted through the bin wall, the risk of the suction tube becoming blocked is additionally even greater. Additionally, the suction tube opening cannot follow the decreasing filling level of the pourable material in the bin, which means that, in this case, a relatively large residual quantity also remains in the bulk material container, which has to be extracted in another way.
Owing to these disadvantages, it is necessary for the bins to be monitored permanently by operating personnel and for the suction pipes to be adjusted manually, if appropriate.
In order to compensate at least partially for the disadvantages mentioned above, it has also already been proposed to provide pulsation and
REFERENCES:
patent: 3951462 (1976-04-01), De Francisci
Fritz Walter
Wilhelm Klaus
Bower Kenneth W
Ellis Christopher P.
Wilhelm Klaus
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