Development of an Auto-Doffer for Covering Machines: Part 7 : Success Improvement and Air-Power Saving on the Yarn Drawing-in Based on Analysis of Yarn Running Behavior

摘要

It is important to improve the rates of success on drawing-in operation of the auto-doffer for the covering machine. Saving air consumption for drawing-in operation can bring about the total energy saving on the doffing operations. In this report, various conditions on the drawing-in operations are investigated in order to improve its success rates and to reduce its air consumption. Experiments were performed with changing supplied pressures for the injector and for the ejector, yarn feed speeds and their working time. Acting forces such as the air drag on a spandex yarn were measured and the behaviors of a running yarn were observed during the drawing-in operations. Results obtained are as follows : (1) Each yarn has the unique drawing-in condition in order to improve the rate of success. The higher pressure does not always bring about the higher rate of success for the injector, but for the ejector within the limits of these experiments.(2) The fine tuning in the working time of the injector or the ejector is not so significant because the yarn in the hollow spindle is extended cyclically by the turbulent air flow. The governing factor for the successful drawing-in operation is the yarn capture at the suction entrance. Yarn feed tuning by means of some pooling devices is prefer to the yarn feed rollers.(3) The velocity of air jet from subsonic to sonic region is the most efficient for drawing-in operation. Further pressure causes the air flow disturbance that may induce the yarn troubles.