Aerodynamic dancer and tension transducer in web handling.

摘要

Scope and method of study. The purpose of this study was to develop an aerodynamic dancer and a tension transducer that are effective in a wide frequency range and do not cause excessive lateral web deflection, touching, or flutter. Both analytical and experimental methods were used and compared. An aerodynamic model of air-turn bar has been developed. The model can handle air-turn bars that have varying density of air-emitting holes. The model predicts the average flotation height of the web, cushion pressure profile under the web, the flow rate, and web tension for given operating conditions. An air dancer model has been developed based on the aerodynamic model of air-turn bars. Experimental verification of the aerodynamic model for the air-turn bar has been done with a stationary-web test setup. Measurements and comparisons were done on the air gap profile, the pressure profile, and the flow rate of air consumed by the air-turn bar. Also examined was the possibility of using an air-turn bar for determination of web tension. For that purpose, the applied web tension was compared with the value determined by multiplying the average cushion pressure under the web by the radius of the air-turn bar. Dynamic testing of dancer systems was done and compared with analytical studies.; Findings and conclusions. It was shown that the air dancer system works well in the web line without any undesirable effects such as excessive lateral deflection of the web, touch-downs, and flutter. It was shown that the air dancer system has a much wider useful frequency range than the conventional dancer system due to its smaller mass and no rotational inertia. It was shown that the air dancer system is effective in reducing tension fluctuation, even near or above the resonant frequency of the system because of the air damping effect. It was shown experimentally that the average cushion pressure was almost the same as long as the web tension was kept at the same value. This means that the web tension can be measured by averaging the cushion pressure between the air-turn bar and the web. The web tension measured by the cushion pressure was within 5% accuracy throughout all the test conditions, up to 1.5 lbf/in of web tension. This shows the feasibility of air devices for web tension measurement. The non-contact tension measurement was shown to work well even in dynamic operating conditions.