Kinetostatic analysis of variable lead screw mechanisms with 3° conic frustum meshing elements

The main concern of this paper is the theoretical kinetostatic analysis of a variable lead screw mechanism (VLSM) used in high speed shuttleless weaving looms. The mechanism consists of a slider-crank submechanism, with four conic frustum meshing elements (with a 3° conical angle) installed in the slider to drive the oscillatory motion of the variable lead screw. It is the spatial cam joint between the meshing elements and the screw. Then, dʹAlembertʹs principle and theory of conjugate surfaces are applied to develop the models for the kinetostatic analysis; models for analyzing the frictional forces of various kinematic joints are also implemented. The result is a set of 27 nonlinear equations with 27 unknowns. The power equation is also applied to analyze the input and dissipated power of the VLSM, its results are also used to check the correctness of solutions to the nonlinear equation set. The VLSM is analyzed for a specified constant input speed or a measured state of motion of the crank. The results show that the peak input power and the peak input torque at constant input velocity are almost twice that of their values at nonconstant input velocities. There are 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 frictional forces.