Desenvolvimento e avaliação de um dispositivo para derriça de café

• Autor(a) principal: Oliveira, Marcus Vinícius Morais de
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/3553
• topic: Derriça de café; Projeto de máquinas; Cafeicultura de montanha; Coffee harvesting; Machine design; Coffee mountain; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA

The coffee harvesting process consists of the following stages: soil surface cleaning, fruit detaching, fruit collecting, collect, pneumatic fruit cleaning and transport. Fruit detaching is the most expensive stage and demands most part of the time during the harvesting. That is why its mechanization is so important. Labor scarcity has been the greatest problem in the regions where the harvesting is semimechanized or manually performed. Because it is a hard work, workers for this job are hard to find, which raises the harvesting cost significantly. The objective of this work was to design, build and evaluate a coffee detaching mechanism that presented more advantages than the current harvesting methods. The prototype consists of a chassis where the detaching mechanism was installed. It is formed by a set of sticks with100 mm and 50 mm spacings between them and mounted in a metallic plate with an area of 0.09 m2. The stick vibration was achieved by an eccentric shaft and a connecting rod, capable of varying the amplitude by changing the length of the eccentric. For the rotation variation, it was used a frequency inverter and a three-phase electric motor with a power of 3.7 kW. An energy generator supplied all systems during the tests performed in the coffee cultivation farm next to the city of Viçosa - MG. To describe the kinematics of the detaching mechanism, some equations based on the theory of Denavit-Hartenberg had been developed and compared to the design developed in a software program. The harvest efficiency was evaluated in the field using different frequencies of vibration and amplitude during a time interval. The utilized frequencies were 15, 17 and 19 Hz, and the vibration amplitudes were 20, 30 and 40 mm. For each canopy of the detached plant, the leaves and branches that had fallen in the soil during the harvesting were collected and measured. The detaching mechanism was located perpendicularly to the coffee tree in a unique point, where the branches were parallel to the vibrating sticks. Two tests had been done changing the number of sticks, sixteen in the first test and forty-nine in the second test. In the first test, the best efficiency was 47.56%, with a frequency of 19 Hz and 20 mm of vibration amplitude. However, this frequency did not differ significantly from the other amplitude. The frequencies 17 and 15 Hz were better in the vibration amplitude of 30 and 40 mm, respectively, for the significant minimal difference at 5%. The leaf and branch detachment did not present a significant difference for the same test of significance, leading to the conclusion that it was a satisfactory result, the fall of leaves and branches was the same for all vibrations, presenting an average of 0.172 kg L-1. In the second test, the ripeness stage was advanced without presenting any significant difference in the efficiency between the treatments. However, the efficiency average increased from 29.82% in the first test to 67.60 in the second test, which can be attributed to the greater number of sticks and to the advanced ripeness stage.