KINETOSTATIC ANALYSIS OF VARIABLE LEAD SCREW MECHANISMS WITH 3(DEGREES) CONIC FRUSTUM MESHING ELEMENTS

The main concern of this paper is the theoretical kinetostatic analysi s of a variable lead screw mechanism (VLSM) used in high speed shuttle less weaving looms. The mechanism consists of a slider-crank submechan ism, with four conic frustum meshing elements (with a 3 degrees conica l angle) installed in the slider to drive the oscillatory motion of th e variable lead screw. It is the spatial cam joint between the meshing elements and the screw. Then, d'Alembert's principle and theory of co njugate surfaces are applied to develop the models for the kinetostati c analysis; models for analyzing the frictional forces of various kine matic joints are also implemented. The result is a set of 27 nonlinear equations with 27 unknowns. The power equation is also applied to ana lyze the input and dissipated power of the VLSM, its results are also used to check the correctness of solutions to the nonlinear equation s et. The VLSM is analyzed for a specified constant input speed or a mea sured state of motion of the crank. The results show that the peak inp ut power and the peak input torque at constant input velocity are almo st twice that of their values at nonconstant input velocities. There a re obvious changes in the bearing loads when the slider is at both of its limit positions due to the change in the directions of the frictio nal forces.