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University of Arizona (1967)

Response of the citrus fruit-stem system to fruit removing actions

Rumsey, James Warren

Titre : Response of the citrus fruit-stem system to fruit removing actions

Auteur : Rumsey, James Warren,

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 1967

Résumé partiel
The past decade has seen many advances in harvest mechanization of many of our agricultural crops. Recent years have seen a concentrated effort by many investigators to mechanize the harvest of citrus fruits. A complete harvest mechanization system for citrus does not exist at this time. A deterrent to the development of such a system has been the lack of basic data on methods of removing the citrus fruit from its stem. The citrus fruit can be removed from Its tree by application of forces on the fruit-stem system. These forces may be applied directly to the fruit itself by, for example, grasping and pulling on the fruit. Forces can be indirectly applied to the fruit when the fruit-stem system is vibrated and inertial forces are developed. The latter two means of applying forces to t W fruit-stem system deal with forces applied to the fruit itself. These forces must result in one or a combination of tension, bending, or shearing stresses being developed across the button of the fruit of such a magnitude as to cause fruit removal. The second means of applying forces to the fruit-stem system is to apply forces to the stem. Gutting the stem is used to detach the fruit from the fruit-stem system. Here shearing forces induced by clippers result in severance of the stem and the fruit is removed. In this study the removal of the citrus fruit from Its stem by torsional, vibratory, and pulling actions has been considered. Removing forces were applied to the fruit itself. Removal of fruit by forces applied directly to the stem (as in cutting the stem) were not considered. The torsional and pull tests were conducted such that the individual and additive effects of tension, bending, and torsional stresses could be observed. Vibrational tests on the fruit-stem system were conducted to gather basic data and observe the response of the system to vibratory removal actions. Results of pull tests have shown that trends of removal pull force throughout the growth and maturation of the citrus fruit are characteristic of the particular citrus variety. It was also shown that when "pull forces are applied at an angle to the major axis of the fruit the magnitude of the removal pull force is substantially reduced. Torsional removal tests have shown that removal torques are independent of maturity of fruit and Independent of amount of tension (up to 10 pounds) that was placed on the stem at the same time the torque was being applied to the fruit. In other words, for a particular variety, the removal torque remained constant throughout the test season. Vibratory removal tests have shown that Marsh grape fruit require a less severe shaking action to cause removal than do Valencia oranges.


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