What Is a Vacuum Actuator?

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  • Written By: Paul Scott
  • Edited By: E. E. Hubbard
  • Last Modified Date: 12 November 2019
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A vacuum actuator is a mechanism that supplies a switching or activation force to a secondary device via the vacuum-induced movement of an internal piston or diaphragm. These actuators are typically found on machinery or processes that produce vacuums during operation, such as automobile engines. The vacuum actuator consists of a small, sealed chamber equipped with a close-fitting piston or captive diaphragm. An actuator rod is attached to the piston or diaphragm, and passes out of the chamber to connect to the secondary device. A port on the chamber is connected to the vacuum-producing part of the machinery, and, when the vacuum increases to a set point, the piston is sucked towards the port, thereby providing the intended actuation force.

Actuators supply remote work by switching, moving, or activating secondary mechanisms. There are many different types of actuators, ranging from simple electromagnetic solenoids to high-precision servo actuators. These devices rely on a variety of power sources to supply their outputs, including electric current, hydraulic pressure, or compressed air. The vacuum actuator is a very specific type of actuation device that utilizes a vacuum source from the actuated system to power its output movement. Common applications for these actuators include various engine functions in automobiles and component activation in air conditioning systems.


The basic principle on which the vacuum actuator operates is fairly simple and may be seen in practice in the common drinking straw. When suction is applied to the straw, a vacuum is created in its interior that pulls the liquid up towards the suction source. The vacuum actuator consists of a hermetically-sealed chamber fitted with a piston or diaphragm in its interior. The piston or diaphragm is, in turn, connected to the actuator rod, which transfers the output motion to the relevant system component.

The chamber of the vacuum actuator is equipped with a port on the side opposite to the actuator rod. This port is then connected to the vacuum source. When the vacuum increases, it draws air out of the chamber pulling the piston or diaphragm towards the port in the same fashion as the beverage in the straw. As the piston or diaphragm moves, so does the actuator rod, supplying the actuation movement in the process. The extent and duration of this movement is entirely dependent on the magnitude of the vacuum, making the vacuum actuator capable of very accurately translating input forces to generated output.


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