One reliable method of handling this task is through a Cam Switch from Candy Controls, Niles Ill. (candycontrols.com). The switch can vary on-off cycle times, as well as dwell time, without custom-designed cams. Technicians can advance or retard the timing, even when machinery is running, to ensure dwell modes activate at the right point in the cycle.
The switch consists of an input shaft, rotating cam, switching mechanism, and dwell and timing controls. When the input shaft turns, it rotates the cam via a parallel shaft and helical gear assembly. The cam has a physical, uniformly increasing rise that rotates over a snap-action switch or air valve. When the switch's roller hits the rise, the circuit trips off. As the cam continues to spin, it lets the roller fall off the rise and turns the circuit off.