The speed of a motor 8 driving a web traction roll 120 is controlled in dependence upon the sensed angle of an arm 106 carrying a jockey roller 100, the tension in the web 140 thus being regulated. A computer control system can set the desired value of web tension, via a signal to pneumatic cylinder 105, and set a nominal speed for motor 8. The system receives a signal representing the angle of arm 106. Traction roller 120 is provided with devices (figure 4) for sensing web wrapping around the roller, as it might after a tear. The motor 8 is stopped and cutting devices 145 and 146 are operated if such wrapping is detected. <IMAGE>
