Abstract
IT seems that the sorting out of foods by the reflection of light will soon be used in regular commercial practice. It is certainly quite feasible for sorting out foods the quality or maturity of which depends on their colour. Science Service has issued a description of a bean elevator that sorts out white pea beans by means of a photoelectric tube. The device is in use in Lowell, Michigan, and it is said that the plant could be adapted for the sorting of peanuts, coffee, almonds and other foods in which colour is the determining factor when making a selection. It is also possible to sort red kidney beans, green peas and other food crops as easily as white beans are now sorted. A battery of a hundred photoelectric cells is used in the Lowell elevator. It operates with such precision that even although the discoloration of the bean is barely discernible to the human eye, it is rejected with high precision. The individual machine is quite small, consisting of a drum with a series of small holes in the rim. Each bean passes in review before a photoelectric cell. The cell accurately measures the reflection of the light from the bean on it. If the light varies, an electric impulse is transmitted to a thyratron tube which permits sufficient current to pass to operate an electromagnet with a trigger-like hammer at one end. Beans not of the proper colour are dislodged from the vacuum drum by the hammer while good white beans pass into a hopper. The sensitivity of the amplifier can be adjusted until practically only white beans pass undisturbed. Each machine can do as much work as six girls hand-picking beans. A similar device might probably be used for sorting out buttons and other coloured objects.
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Sorting Foods by Reflection of Light. Nature 132, 963 (1933). https://doi.org/10.1038/132963b0
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DOI: https://doi.org/10.1038/132963b0