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Applying some TRIZ concepts to the problem of harvesting and selection of potatoes

José M. Vicente-Gomila,
Co-Director of triz XXI
Assoc. Lecturer in the Project Engineering Dept. of the Polytechnic University of Valencia
vicente@triz.net, www.triz.es
Valencia, SPAIN
Victor Esteller Leal,
Technician, triz XXI.

It is known that harvesting has become increasingly automated, improving productivity and reducing human intensive labour. However, despite these efforts for automation, some areas still need improvement and new ideas. An example of this is a stage within the process of potato harvesting- the process used in the separation of freshly harvested potatoes from soil lumps, stones and other undesirable byproducts.

Although there are a few patents relating to this process, the results are not satisfactory, thus new patents are being applied and published from many different countries. The state of the art is based mainly in trying to take advantage of any difference between potatoes and other bodies. Thus, one can find patents based in the shaking and sifting of the gathered matter in order to take advantage of the different resting positions of the root, and the plant and loose ground can then be easily removed using these methods. However, such methods are not effective in separating stones or in the even more difficult process of separating soil lumps. Patents with such a focus are for example, US5425459 “ Stone separation table for potatoes and other root crops “ or US3625290 “Separating apparatus for mobile potato harvesting vehicle” that uses water as a means to separate by density differences.

Altshuller (1), father of TRIZ and theoretical mentor of TRIZ practitioners, reminds us of the limited value of concentrating on physical differences in his example of the separation of wooden chips into wood and bark, instead of applying a true S-field.

In this sense, others applying (probably without noticing) S-fields, try to look for different techniques. There are curious methods using different fields like acoustic fields, even nuclear fields or X-rays fields. Although these apply s-fields to some extent (beam, potato or body and a detector), most of the time they focus on differences which are not significant, allowing inaccuracy in selecting potatoes.

Within this category we can find patents like US4466543 “ Method and device for distinguishing between field crops, particularly potatoes on one hand and stone or clods of soil on the other hand.” that uses a magnetic field for distinguishing potatoes, or US3675769 “Method and apparatus for separating potatoes from stones and soil clods” which uses two light beams one visible and one infrared as fields, or US4466543 which uses an acoustic field to detect different responses to said field. Patent USRE31660, uses a mechanical field, vibrations, to see the differences betwen the response of potatoes or stones to that field. The Spanish patent 2112118 allows potatoes and lumps or stones fall onto a membrane whose vibration produces different sounds enabling the selection.

All these patents use fields but only take advantages of the different responses to the different fields used.

Let us try to make a functional analysis of the problem using Invention Machine’s TechOptimizer 3.5:

Instead of focusing on differences let us start applying TRIZ, both Altshuller’s inventive principles and S-Fields.

If we use the engineering parameters to improve some of the following:

And cross -reference several of the following parameters as the worsening features:

The matrix presents us with the following principles which we will now consider:

Principle 22 states that if something produces a harmful action then increasing the harmful action may be beneficial. This focuses our attention on the inherent moisture and the soil lumps. If some water causes the formation of the soil lumps, an excess of water can benefit not by easing the selection but by clearing the lumps! Thus eliminating the need for selection.

As we can see the matrix directs us to a different concept, instead of sorting out and separating the problem, let us make the problem disappear. Now our focus should be not in differentiating but in destroying or ‘dissolving’ soil lumps. As humidity is not advantageous for string potatoes, we should dry the potatoes afterwards. Using existing resources, we could use air heated by the harvesting machine engine, to dry the potatoes.

TRIZ is a very comprehensive method because we could have arrived at the same conclusions using different ways like using S-fields and the 76 standard solutions or simply by using the TRIZ based TechOptimizer Software trimming function. We could also arrive at similar conclusions using the ‘object removal’ technique and the ‘unification’ technique of A.S.I.T¹.

To destroy the lumps in a water medium we could address differences in mechanical fields, among other solutions, displayed in the functional tree of the TechOptimiser software, like ultrasonic vibrations or acoustic waves. If we take the evolution trends, we could think of utilizing the mean frequency of the lumps and use resonance to destroy them, provided it is not the same frequency as the potato!

Phenomena like cavitation, bubbles or the force of water jets could also be applied to destroy lumps without destroying the potatoes, thus making separation afterwards, very easy.

If we take inventive principle 22 segmentation, especially the sentence “make an object easy to disassemble”, we could try to make lumps easy to disassemble (still inheriting the idea of clearing instead of sorting). Everybody can think of a possible solution but let us resist the temptation and go further with the method

Principle 9 and 10 may also give us the idea to prepare the soil at the start of the process, when seeding, before harvesting. If there is a harmful action (building up of lumps) let us prepare a counteraction.

Taking the S-field model, we have a ‘bad’ S-field:

Then we can apply for instance, standard solution nº 1.2.3

For example, spreading some cheap polymer (see recycled materials) ‘pearls’ or particles to the ground, that disturb the structure of the lumps, preventing them, without distorting the ability of potato roots, to absorb water and nutrients, and thus make it easy to dissolve any remaining lumps, later on.

These are only a few ways to apply standard TRIZ principles, and enhanced with the help of tools like Invention Machine’s TechOptimizer, many expert solutions could be applied to the processing problem. There are plenty of areas where TRIZ can be applied to uncover new approaches. Advances need change, and new ideas are needed for that change to become reality!

Endnotes:
1) Dr. Ron Horowitz, www.start2think.com.

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