旋耕机与旋耕刀.pptVIP

Rotary TillersAnd Rotary Blades Background Rotary tiller (rotary hoe) is widely used for soil cultivation In south of China, more than 80% soil tillage work is finished by rotary tillers An Innovation in Australia A long row to hoe The Howard Rotavator ? In 1912, 16-year-old Cliff Howard had an idea that would change the way small farms were cultivated. To make hoeing more efficient, Howard introduced power to the hoe’s blades, so that they would dig the earth and help push the hoe forward at the same time. All the farmer had to do was steer. Howard Rotavator It took ten years for Howard’s first Rotavator to be perfected. At their sales peak in 1970, 100 000 a year were exported to 120 countries. A Problem When rotary tillers are used in very grassy paddy fields, in which soils are soft and grass difficult to cut, grass and straw twists on their rotary axles and rotary blades thus preventing rotation Research Aims Overcome the above problem, preventing grass and straw to twist on rotary blades Evaluate grass-removing performance of rotary blades with grass-removing angles Calculate magnitude of grass-removing angles Help design rotary blades with better grass-removing performance Rotary Blade When a rotary blade is cutting into soil, the edge of the blade can be considered as a cutting edge At any point of the edge curve, a tangential line can be used to represent the cutting edge of that point Slide-cutting Dividing velocity v into vt and vn The ratio vt / vn = tan ? ? is called the slide-cutting angle Grass-removing Angle If ? has a large value, grass and straw can slip easily off the blade For rotary blades, ? is the grass-removing angle Analysis of Slide-cutting Dividing N into T and P T = N tan ? , F = N f = N tanψ If T ＞ F , then ? ＞ψ Analysis of ? ? is the angle between the velocity and the normal line of edge curve The absolute velocity is the resultant of linear velocity r? and forward velocity u ? can be divided i