Bobbin yarn reserve - uses unwound preset length drawn into a store by the doffer and then rewound at the head end of the bobbin

摘要

To form a yarn reserve winding on a cross-wound bobbin, pref. at the head end using the doffer, a pre-set yarn length is used as the reserve, which is unwound from the bobbin to be held for itnermediate storage. A sensor registers that the yarn reserve length is present in the store. When the required length has been unwound, the bobbin is stopped and its rotation is reversed back into the winding direction while the reserve yarn length is positioned at the head end and wound round the bobbin at this section through the bobbin rotation. As the yarn reserve length is drawn out of the store, a brake action is applied to maintain the reserve yarn tension. The yarn unwinding from the bobbin is pref. stopped when it is registerd by the sensor, or, when the sensor registers the yarn, the bobbin unwinding is stopped after a given time delay. The search for the yarn end, at the cross wound bobbin, is stopped when the sensor has not registered its presence after a given time span and a fault signal is generated. The reciprocating movement of the yarn in the store is generally suppressed and positioned at the head end of the bobbin to be in the right place for rewinding as the reserve and any surplus length is trimmed. A sensor positions the yarn at the head end of the bobbin. A suction air stream is used to search for the yarn end at the bobbin, which also draws the yarn end into the store, through a suction tube applied to the surface of the wound yarn on the bobbin.