Rieter

Cone drive transmission

Index

Variation of the bobbin rotation speed originates in the cone transmission and occurs in small steps through shifting of the cone belt after each lift stroke. Bobbin rotation must be changed in accordance with a linear function. Unfortunately, shifting the belt by constant amounts on straight-sided cones does not vary the transmission ratio in a linear manner and thus does not produce the required linear variation in bobbin rotation speed. To obtain the desired linear variation function, the cone faces have been made hyperbolic (see Fig. 19), namely convex on the upper driving cone and concave on the lower driven cone. Hyperbolic cones are difficult to design. Additionally, during the winding operation, the belt is then always moved on surfaces of varying inclination. As a result cones are now mostly made straight-sided. However, in transmissions of this kind the belt must be shifted through steps of varying magnitude, the initial steps being relatively large (Fig. 20, W1) and the later ones smaller (W4). Instead of a hyperbolic profile on the cones (left), an eccentric is used in the belt-shifting mechanism (right).

Fig. 19 – Convex and concave cones

Fig. 20 – Shifting the belt with hyperbolic (a) and straight-sided cones (b)