Influence of the shape of disk knife on the pinching of material

Abstract

During the primary cultivation by means of general-purpose ploughs, the circular disk knives do not provide a reliable cutting; with that, the traction resistance of plough is increased, productivity and quality of its work are reduced. The purpose of the research is to increase the operational efficiency, the quality of soil cultivation and to reduce the energy intensity of general-purpose ploughs equipped with disc knives. Different designs of knives are studied in order to find the optimal shape providing a reliable pinching of plant and straw mass. A formula for determining the angle of pinching of a polygonal disc depending on the cultivation depth and number of angles in the polygon is given. The studies show that the hexagonal disk knives have the minimum angle of pinching, thus this shape is rational. The operating conditions are defined, in which the stalks of straw mass do not slip out of the knife blade when cutting. Motion paths of blades of hexagonal and circular knives at different positions of the instantaneous center of disk rotation are studied graphically. An empirical formula is obtained; dependences of pinching coefficient on the position of instantaneous center of disk rotation are constructed. It is found that with decreasing of nominal diameter of a knife the pinching coefficient is increased, and the quality of pinching of crop materials is improved. As a result of the research, the dependences are obtained showing that the areas of reliable pinching and cutting linearly depend on the kinematic parameter. With the cultivation depth of 0.08-0.12 m, the efficiency of pinching of hexagonal knife is increased by 1.8-2 times compared to the circular one.