Rieter

The active pneumatic system

Index

In a normal card, a funnel is provided before the calender rollers (2, Fig. 133) in order to collect the web into a sliver. In Zellweger equipment, this funnel is developed to form a measuring device based on a simple physical principle. When fiber material enters the funnel (3), it carries along quite an amount of air held between the fibers. Owing to the continuous convergence of the funnel, air is squeezed out as the material passes through.

This generates air pressure in excess of atmospheric pressure, which is a function of the sliver cross-section if the sliver speed is kept constant. If all fiber characteristics also remain constant, this pressure is proportional to the volume. A lateral bore (5) in the funnel, and corresponding leads, transmit the pressure into the chamber of a pneumatic-electrical pressure transducer, using electrical induction to convert the pressure into an electrical signal.

Comparison of the signal with a set value enables pulses to be generated to control the electronic units in the regulator equipment. The advantage of active pneumatic measurement lies in the simplicity of the system, which does not require additional and/or sensitive moving parts. The disadvantage is that measurement is affected by the fiber count and hence count variation can lead to errors.

Fig. 133 – Active pneumatic measuring system (Zellweger, Uster)