Design of a lifting mechanism for a rotary electronic dobby and an analysis of the shedding craft

Abstract

To meet the craft requirements of the heald-frame dwell time and the dynamic characteristics during warp shedding, a method for constructing a variable-speed function is proposed based on the cycloid function. Subsequently a parameterized model of the rotating variable-speed motion and a comprehensive model for the size of the heald connecting rod get established with the modulator function. Additionally, the offset coefficient gets identified as the only control variable in this function. Besides, the influence of the variable-speed motion of the lifting mechanism on the process characteristics of the shedding can be verified under different parameter conditions through experiments and simulations. The results show that when the swing angle of the lifting arm is constant, the heald-frame dwell time, speed, and acceleration decrease along with the increase of the offset coefficient. Through adjusting the offset coefficient, dwell times of different heald-frame and its dynamic characteristics can be obtained to satisfy the need of different weaving processes. When the offset coefficient is 0.41, the heald frame stopped at approximately 120° relative to the loom main shaft and the shedding symmetry rate reached 94.83%. The motion characteristics of lifting mechanism are fine at this time, which can provide a theoretical reference for the design of multi-arm shedding system.