Linear Actuation Through a Pressure Boundary


By John Meyer, Senior Business Development Manager, Senior Aerospace

There are many applications for linear actuators within the vacuum environment including pin lifters, wafer lifts, shutter valves, and others. The challenge is how to provide linear actuation through a pressure boundary while maintaining the hermetic integrity of the chamber.

One linear actuator has been developed that combines the actuation and dynamic sealing functions into one unit. It is the metal bellows type Prime Mover actuator. It is integrated into a device to act as the hermetic seal and as the actuation force generator. When a pressure differential is applied across the bellows, it will compress and thus drive the actuator. When the pressure is removed, the bellows spring force will retract the actuator. The all welded construction provides a completely hermetic seal.

The metal bellows type Prime Mover actuator offers some advantages in cost and performance. The device is compact combining both the sealing and actuation functions into one unit, allowing for an overall more compact equipment design.


Because there are no wearing seals, the Prime Mover is maintenance free and can operate for millions of cycles without failure.

This actuator can be made to be adjustable but it is not necessary. It can be factory preset to specific actuation requirements, which can simplify installation into the system as no adjustment or calibration is required. System level integration is simpler and the system component count is reduced.

Prime Mover offers axial motion and no rotational forces are introduced. Since the actuator uses all metal construction, it can be used in temperature extremes, cryogenic to 450° F. Additionally, the all-metal construction makes it compatible with the harshest chemicals, plasmas, and fluids.

These actuators are accurate and repeatable. Up and down stop Z-axis positional accuracy is ±0.001-in., lateral positional accuracy is ±0.005-in., and repeatability is ±1 0.0005-in. Unit-to-unit uniformity is within 0.005-in. over the entire stroke.

The Prime Mover is designed for 60-90 PSID pressure range, which produces actuation forces on the order of 40 to 80 lb. With larger diameter actuators, actuation forces of up to 1000 lb can be achieved. Because there are no wearing seals, the actuator can be designed for 10 million cycles or greater. The actuator meets ISO 14644 Class 1 requirements.

Senior Aerospace

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