JAG actuators work with scotch yoke system.

This system is having a longer „arm“ and offer a much higher torque at beginning and end of stroke respect to rack and pinion actuators with same piston diameter.
The torque curve corrispond perfectly to the variable torque curve of a ball or butterfly valve.
In that way you can often choose one smaller size of the scotch yoke actuator compared with rack and pinions actuators.
This reduce the costs for the product, air consumption as well as dimensions and weights.

Power transmission

Air pressure on the piston will transfer the power throughout the bush to the crank which is fixed connected to the stem and so to the valve´s stem.

The lever L is the longest at 0° and develops the highest torque when closing (as needed for ball and butterfly valve). In the middle position the lever is the shortest and increases again when opening (as needed for ball valves).

Torque diagram

It is a typical property of scotch yoke actators to have an up to 50% higher torque than rack and pinion actuators in the ends of the stroke. The torque curve of the JAG spring return scotch yoke actuator shows an increasing torque in the spring return position (safety position), where a safe function is needed.