With the essential design elements of the rack and pinion, the rotary movement is produced from the linear movement of two reciprocating pistons. The racks of the two pistons are engaged with the pinion, which transmits the rotary motion to the armature.
The piston movement is effected by compressed air on the piston surfaces.
The transverse forces occurring during the sliding movement of the pistons are absorbed by guide rods. This ensures a perfect axial guidance of the pistons, so that the piston seals function well and permanently. The principle of rack / pinion results in a uniform torque course during the shifting process due to the constant effective distances between the rack and pinion.
For AMG SAD actuators, the movement is generated with compressed air. When the outer chambers are ventilated, the switching shaft rotates clockwise (fitting closes). When the internal chamber is ventilated, the switching shaft rotates counterclockwise (valve opens).
AMG quater-turn actuators of type SAF are moved with compressed air and spring force. For single-acting actuators, only the inner chamber is pressurized. The force generated thereby not only moves the fitting in one direction, but at the same time tensiones safety springs for the return. The spring force is able to move the valve into the safety position "CLOSE" or "OPEN" in the event of a failure.
