Abstract: Traversing mechanism for use in any type of machine in which part of the machine is required to reciprocate between two predetermined limits of travel. The mechanism includes a carriage which is attachable to that machine part, and an endless belt which, in operation, is continuously driven in one direction and has two parallel runs located on opposite sides of the carriage. A rotatable coupling wheel is mounted on the carriage and has an odd number of radially projecting lobes arranged around its periphery so that in one rotational position of the wheel one lobe engages one run of the belt, and in another rotational position of the wheel another lobe engages the other run of the belt. The arrangement is such that in each rotational position of the wheel there is only one lobe in full engagement with the belt.