Patent Application
20080130401
The present invention generally relates to an apparatus for dosing material, more particularly material such as compost, moss, garden soil, mulch and nuggets. More particularly, the invention relates to a system adapted for the treatment of loose compressible fibrous material, having naturally variable densities and granulometries, with the aim of measuring a specific quantity of the material by volume or by weight.
Precise dosage based on a volumetric or mass basis of bulk loose materials that are compressible, cohesive and isotropic in nature has always represented a challenge in industries having to manipulate and transform such products. Bagging of composts, potting soils and substrates are good illustrations of this problem. For the production of 30 liter bags on a conveyor producing 30 bags per minute, the variation of the average volume being bagged is in the order of plus or minus 10%. Such a variation has very important cost implications. In order to produce bags offering a volume equal or greater than 30 liters in 95% of cases, the manufacturer must aim to have an average amount of 33 liters for those bags. Assuming a hypothetical daily production rate of the order of 12,000 bags, the lack of precision of the dosage system leads to financial losses corresponding to the amount of 36,000 liters of materials per day. One must know that the dosage of a similar type of material on a mass basis offers similar problems of lack of precision.
Presently, equipments used to dose compost, potting soils and substrates are constituted of:
Dosage of materials is based on the control of stop and activation periods. Dosage on a volumetric basis is done through programming of the length of the stop and activation times, while dosage on a mass basis implies the use of a weighing device that causes stoppage or activation of the conveying system.
Variations observed in dosage also results from the nature of the product being manipulated. On one hand, products such as compost, potting soils and substrates are of a cohesive nature that can lead to the formation of aggregates. This phenomenon can be accentuated notably by the level of humidity observed locally. On the other hand, these products are easily compressible. Finally, input materials used in the fabrication of these products often present different granulometries and densities.
Moreover, it should be emphasized that the manipulation of such heterogeneous products in dosage equipment tends to accentuate heterogeneous phenomena. Indeed, one can observe at the level of the buffer container a differential compaction phenomenon depending on the thickness of the product present in the container and the location where the product is situated in the container, as shown in
Furthermore, control of the thickness of the material at the output through a barrier mechanism causes a shearing phenomenon between the material in movement and the more stable material, thus causing the creation of new aggregates and zones of higher density. Displacement through a conveyor mechanism during a certain period of time of a given volume of product having heterogeneous granulometries and densities leads inevitably to variations in the dosed quantity.
It must also be mentioned that the reduced space given to dosage equipment (between 2 and 3 meters) in a transformation or packaging production line, increases greatly the complexity of the integration of a system for homogenization of the granulometry and density of the material in the dosage equipment. Moreover, this complexity is further increased by the fact that one must ensure that production speeds must offer performances of the order of 30 dosages or more per minute. Finally, dosage equipment must also ensure a conservation of a certain level of integrity of the fibrous nature or the texture of the material while ensuring homogeneity of the granulometry and of the density of the material.
Thus, there presently exists a need for a dosage apparatus for compressible materials that reduces variations in the dosed quantities while maintaining high production speeds.
One of the objects of the present invention is to provide an apparatus that addresses this need.
More particularly, the principle of the present invention consists to add, to conventional dosage systems, additional steps for treatment of the material allowing a reduction and control of the variation of the granulometry and density of the material to be dosed before the thickness adjustment step of the material to be dosed. In addition to the three main parts of conventional systems, such as the buffer container, the system for adjustment of the thickness of the material and a material conveying system, the apparatus according to the present invention integrates additional systems located between the buffer container and the thickness adjustment system for the material to be dosed. These additional systems have the function of controlling the granulometry and density of the material before the step of controlling output from the apparatus.
More particularly, the present invention relates to a dosing system for loose compressible material having heterogeneous granulometry and/or density for outputting the material though a main outlet, comprising:
The principle behind the operation of this apparatus is the following: the loose material arrives in the receiving structure through the top and accumulates within the structure. Preferably, a detection system of the top level of the product allows management of the arrival of the material in order to ensure that the receiving structure is never empty, nor too full.
Thereafter, the material exits the receiving structure, by a first conveying system located at the base of the receiving structure, preferably a conveyor belt. The material is then passed, completely or in part, through a homogenizing system. This homogenizing system allows homogenizing of the biggest particles of material from an average dimension controlled by the system. This homogenizing system has the effect of reducing the initial variation in the granulometry and density of the material. Moreover, the same mechanism allows elimination of non-controlled compaction effects of the material associated with shearing phenomena at the outlet of the receiving structure and due to differential pressure exerted on the material under the effect of its own weight.
Afterwards, the material preferably freefalls in a transition volume delimited by the homogenizing system, a leveling adjustment system and a second conveying system. The second conveying system is located at the base of the transition volume, and is preferably a conveyor belt. A detection system allows control of the level of material located inside the transition volume. The detection system maintains the desired level of product in the transition volume through control of the first conveying system speed located upstream thereof. By containing a minimal amount of material, the transition volume allows avoidance of the onset of non-controlled compaction zones that result from shearing phenomena or differential pressure exerted on the material under the effect of its own weight.
According to a preferred embodiment of the present invention, the first conveying system is located at a higher level than the transition volume in order to ensure that the material freefalls through gravity effects into the transition volume and thus ends the homogenizing process.
The material is transported by the second conveying system towards the main outlet of the dosing system. The quantity of material being transported is adjusted by a leveling adjustment system. The volume of dosed material is a function of the distance traveled and of the speed of the second conveying system.
Such a dosage system allows an increase in the levels of precision of the dosed quantity. In certain preferred embodiments, levels of precision of the order of 2% (average plus or minus to standard deviations) can be obtained, which represent increases in precision of the order of 8% with respect to prior art systems.
Advantageously, the addition of a homogenizing system combined with a transition volume, all located between the receiving container and the main outlet of a conventional dosing system allows a reduction and stabilization of the variations in the granulometry and density of the material and thus increases the level of precision of the dosage, all in a reduced amount of space of about 2 to 3 meters, which is normally allocated in prior art systems to dosage equipment for such materials.
The present invention also relates to a method for dosing loose compressible materials and for outputting the material through a main outlet, the method comprising the steps of:
A non-restrictive description of a preferred embodiment of the invention will now be given with reference to the appended drawings.
The elements of the system are identified in the figures by the following reference numbers as described in the table below:
As shown in
A homogenizing system 16, such as a starred-tool device, closes the outlet of the receiving structure 10. This homogenizing system 16 allows homogenizing of the material before its dosage. By homogenizing, one means to give homogeneous properties to the material, wherein homogeneous properties include standard, controlled and constant density and granulometry. Consequently, larger particles of material are divided and given an average dimension, therefore limiting or reducing variations of the granulometry and density of the product. The homogenizing system 16 proposed in the preferred embodiment shown in the figures is a plurality of starred tools, spaced such that agglomerations of material over a predetermined size are separated by the plurality of starred tools before being fed to the transition volume. It should be noted however that any other homogenizing device known to the person of the art can be used without going beyond the scope of the present invention. According to another embodiment, the homogenizing system 16 comprises a plurality of rotating blade devices spaced such that, once again, agglomerations of material over a predetermined size are separated by the plurality of rotating blade devices before being fed to the transition volume 40.
The receiving structure 10 allows containment of a variable volume of material to be dosed through time. The mechanical drive 14 drives the belt of the first conveying system 12. By advancing, the belt of the first conveying system 12 carries the product contained in the receiving structure 10 towards the homogenizing system 16. (Element 50 in
Preferably, the first conveying system 12 is located at a higher level than the transition volume 40 such that the material can freefall by gravity in the transition volume 40. The height difference is preferably of the order of 18 inches. The level of material in the transition volume 40 is controlled by a second level detection system 22. A second conveying system 24 is located under the transition volume 40. The material in the transition volume 40 is thus supported by a belt of the second conveying system 24. This belt moves thanks to mechanical drive 26. This mechanical drive 26 is preferably provided with a servomotor allowing control of speed in a precise manner. It should be noted however that in another embodiment of the invention that is not shown, the first conveying system and the second conveying system can be placed one after the other and may constitute one single conveying system including the homogenizing system and the transition volume. Preferably, the dosing system comprising a controller for controlling a material displacement speed of the first conveying system 12 based on a measurement of the second level of material contained in the transition volume 40 made by the second level detection system 22. For example, the material displacement speed of the first conveying system 12 can be increased if the second level of material decreases below a given threshold.
By advancing, the belt of the second conveying system 24 transports the material against the leveling adjustment system 28. Lateral walls 20 close the two sides of the second conveying system 24. These walls 20 are preferably parallel and vertical but could have a slight angle towards the outside of the system and the direction of travel of the material.
Preferably, the second conveying system 24 is also provided with a leveling adjustment system 28 that can be made of several blades fixed on a rotating shaft. This leveling adjustment system 28 is provided with a height adjustment mechanism 42 for adjusting the vertical position of the leveling adjustment system within the dosing system. The leveling adjustment system 28 is rotatively driven by a mechanical drive 32. The mechanical drive 32 is built in order to allow functioning of the leveling system 28 without any adjustments when the leveling system 28 is displaced vertically with the height adjustment mechanism 42.
Preferably, the second conveying system 24 can also comprise a blocking trap 34 near the main outlet 36 and located at an extremity of the second conveying system. The blocking trap can comprise a catch gate used when operating the system on a weight basis and a cutting gate used when operating the system on a volumetric basis. Only one of the catch or cutting gates is used at a time. At this point, the material can either be directed towards other conveyors, weighed or placed directly into bags. Optionally, a weighing bin 46 for weighing a quantity material exiting the main outlet may be provided.
The present invention also provides a method for dosing loose compressible materials and for outputting the material through a main outlet. The method comprises a number of basic steps to which a number of optional steps may be added. The method comprising the steps of:
Preferably, the method further comprises a step of controlling a first level of material contained in the receiving structure.
Preferably, the method further comprises a step of controlling a second level of material contained in a transition volume between the homogenizing system and the leveling adjustment system.
Preferably, the method further comprises a step of controlling a vertical position of the leveling adjustment system within the dosing system.
Preferably, the method further comprises a step of controlling a material displacement speed of the first conveying system based on a measurement of the second level of material contained and detected in the transition volume.
It is to be noted that although a preferred embodiment of the invention has been described in detail hereinabove and illustrated in the appended drawings, the invention is not limited to this single embodiment and several changes and modifications can be carried out by a person of the art without departing from the scope or spirit of the invention.
| Number | Date | Country | |
|---|---|---|---|
| 60859256 | Nov 2006 | US |
