Early weft feeders are mostly moving drums, as shown in the figure. The yarn storage drum 6 rotates around its axis to wind the weft yarn on the drum to complete the yarn winding of the moving drum type weft feeder. The winding tension of the weft yarn is adjusted by the yarn feed tensioner 3. The structure of the weft feeder adopting this winding method is relatively simple.
The damping ring 5 in front of the yarn storage drum is made of bristles or nylon. The damping ring exerts an unwinding tension on the weft yarn, and at the same time it controls the yarn loop on the drum surface, so that the winding movement of the yarn on the yarn storage drum is carried out normally. The damping ring also prevents the possibility of the weft yarn being thrown away from the storage drum to form an air ring when the weft yarn is unwinding, and prevents the weft yarn from tangling. At the end of unwinding, the damping ring constrains the weft separation point on the drum surface to prevent the weft from being sent out excessively. The damping ring is divided into "S" direction and "Z" direction, which is suitable for "S" twist or "Z" twist weft yarn. The diameter of the bristles or nylon filaments is also divided into thick and thin according to the fineness of the weft.
The storage capacity detecting device is used to control the storage capacity of the weft yarn on the yarn storage drum. When the yarn is stored to the position aligned by the photoelectric reflection detection device, the mirror surface is covered, and the detection device sends a signal to stop the yarn storage drum. The size of the storage is adjusted by the position of the movement detection device. The storage capacity affects the quality of the yarn storage. If the storage capacity is too small, the yarn on the storage drum will be emptied. If the storage capacity is too large, it will cause problems such as difficulty in winding, uneven yarn arrangement or overlapping yarns.
When the weft yarn is wound on the storage drum, it is first wound on the conical part of the storage drum, and then slides into the cylindrical part under the action of tension. The cone apex angle of the cone surface has certain requirements, so that when the yarn on the cone surface slides into the cylindrical part, it can push the weft yarns on the cylindrical surface to move forward, forming a regular yarn loop tightly arranged. Since the yarn arrangement work is not done by a special yarn arrangement mechanism, this yarn arrangement method is called a passive yarn arrangement method. The effect of negative yarn arrangement is closely related to the shape of the yarn storage drum. Theoretical research has proved that the yarn arrangement effect is better when the cone apex angle of the cone part of the yarn storage drum is 135°. At the same time, the tension exerted by the feed tensioner on the weft also affects the yarn arrangement effect of the yarn storage drum. Excessive tension will increase the resistance to the forward movement of the yarn loop on the cylindrical surface. If the tension is too small, the yarn on the conical surface will oppose. The thrust of the yarn loop on the cylindrical surface is insufficient.
The speed of the yarn storage drum can be adjusted. In order to shorten the drum stop time as much as possible and make the package unwinding process almost continuous, the speed of the storage drum should be adjusted lower, but the weft supply should be satisfied. The lowest speed of the storage drum is:
nmin=(1＋a)nLk/(πd)
In the formula: nmin———the minimum speed of the yarn storage drum;
n ——— Rotating speed of loom;)
Lk --- the reed width on the loom;
d———the diameter of the winding part of the yarn storage drum;
a—The rate of addition and release considering the selvage and other factors, expressed as a percentage.
The yarn storage drum of the moving drum feeder has a certain moment of inertia, which is proportional to the square of the diameter of the drum. The greater the moment of inertia, the more unfavorable the frequent starting and braking during the weft storage process, so the diameter of the drum should not be too large. The number of yarn turns stored on the yarn storage drum is inversely proportional to the diameter of the drum. Too small a diameter will bring about the disadvantage of increasing the number of stored yarn turns, resulting in difficulty in arranging yarn and overlapping yarn loops. For this reason, the diameter of the drum should be selected appropriately, generally about 100mm.
