Rieter

The formation of the conical layers

Index

It has already been mentioned that the ring rail is not moved uniformly. Its speed increases during upward movement and falls during downward movement. At the tip of each layer the speed is higher than at the base of the layer, i.e. the ring rail does not dwell as long at the tip as it does at the base: less material is wound, and the layer is thinner at the tip. If it is assumed by way of example that the ring rail is moving twice as fast at the top of its stroke as at the bottom of the stroke, the first layer would be half as thick at the top as at the bottom, i.e. b 1/2 instead of b1, (Fig. 88).

The first layer would correspond to a trapezium with the side b1 at the bottom and the side b1 1/2 at the top. This is followed by the deposition of the second layer. Owing to the constant, short-term lifting of the ring rail, the upper portion of the new layer would again be deposited on the bare tube.

The average diameter at the top would be the same as that of the first layer, and the volume, and hence the thickness, would also be the same, that is b1 1/2. Each newly deposited layer will have this thickness of b11/2 at the top. At the bottom, however, the winding diameter is increasing continually so that the layer thickness is declining from b1 to b2 to b3 to b4 . Accordingly, continually narrowing trapezia are produced.

At some stage, the trapezium will become a parallelogram, i.e. the lower side will be the same size as the upper side: both will be b11/2. Since all other winding conditions now remain the same, no further variation can now arise in the layering. One conical layer will be laid upon the other until the cop is full, i.e. when the cylindrical portion of the cop is formed.

The gearing change wheel has little influence on this sequence of events. If too many teeth are inserted, the final condition of constant conical layers will be reached too soon, and the cop will be too thin. It will be too thick if the ring rail is lifted too slowly.

Fig. 88 – The formation of the conical layers