versão impressa ISSN 0006-8705
Bragantia vol.10 no.9 Campinas 1950
A separação dos torrões de terra roxa do café, pelo magnetismo
Engenheiro agrônomo. Secção de Café, Instituto Agronômico de Campinas
In the regions of the so called "purple soils", in the State of São Paulo and Northern Paraná, coffee harvested from the ground is attended by a number of foreign matter among which lumps of soils of varying sizes make up the bulk of it.
The separation of such lumps as attained by mechanical devices usually employed is always not satisfactory, the result being that remaining lumps will give a red color to the coffee beans, thus lowering the
Since the soil lumps have an appreciable amount of iron oxyde, mainly in the form of magnetite (Fe3O4) ; there would appear that the use of electro-magnets or permanent magnets of high power would give good results.
A new machine "catador Dr. Isay" having rotative permanent magnets thus appeared in the market and tests were officiary run to determine its perfomance. It was verified that such machine performs a good job in the separation of small lumps, just the ones which are not efficiently separeted by other types of machines usually employed like "washers" (lavadores) "assorting machines" (seletores), and "stoners" (catadores de pedra).
A theoretical study of the new machine "catador Dr. Isay" was also perfomed, showing that the following factors are likely to have an important bearing on its performances : a) centrifugal force to which the lumps are subjected which is dependent upon the velocity of the magnetic rolls and the lumps effective size ; b) shape of the "entre-ferro" ; c) characteristics of the material employed in the manufacture of the permanent magnet. In this respect it seems advisable to recommend the use of alnico alloys, mainly class 5 and 6.
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1. Goss, J. H. Ductile permanent magnets offer new design possibilities. Reprinted from Product Engineer, January, 1946. [ Links ]
2. Guillaumin. J. B. Les aimaiits permanents et le nickel. Revue du Nickel 16 : 79-90. 1950. [ Links ]
3. Hicks, C. L. Nickel-Iron alloys for magnetic circuits. Reprinted from electrical manufacturing, January, 1946. [ Links ]
4. Luerssen, G. V. Iron-Nickel alloys and their characteristics. Reprinted from Electrical Manufacturing, July, 1945. [ Links ]
5. Quittkat, G. et al. Em Hutte. Manual del Ingeniero, 4 : pág. 456, 2.ª ed., Gustavo Gili S.A., Barcelona, 1942. [ Links ]
6. Tosello, A. Ensaios sôbre o catador "Dr. Isay". Relatório da Secção de Café do Instituto Agronômico, 1950, (não publicado). [ Links ]