A piston actuator, like all actuators, is a device that transforms raw energy into motion. In general, the actuator is connected to a piston which is contained inside an enclosure. Something that causes pressure will enter the enclosure and force the piston to move, which moves the actuator and whatever it is connected to. With a proper design, it is possible for this motion to continue through a series of steps and parts resulting in a large amount of motion generated by a small change in the actuator itself. In most cases, these devices are powered through pneumatic, hydraulic or combustion systems.
As stated above, the design of a piston actuator is quite simple. Most of them only consist of a few parts — the piston, the enclosure and the actuator arm — along with two valves to let the energy source in and out. The most complex part of the system is typically the method used to protect the piston from the energy source.
Regardless of what moves the piston, the inside of the enclosure must be as close to airtight as possible to get the biggest return on energy use. Most of these systems use a cylinder with the piston head making up one end. Since the energy within the enclosure is designed to cause bursts of pressure, even the smallest leaks around the valves or piston can cause a lack of power. Some enclosures also have to protect the inside of the system from hazards such as extreme heat or water damage.
The size of the piston actuator is in direct proportion to the amount of energy needed to move it and the amount of motion it can create. A large piston actuator requires a great deal of power, while smaller ones don’t. A small piston generates a small amount of movement and a large one generates a lot. While this may seem obvious, it comes into play when a system uses a process that can multiply power output, which is a practice common in hydraulic systems.
Many types of piston actuators use hydraulic systems for that very reason. Small pistons are connected to a larger tank containing a large piston. The small pistons will activate and move a relatively small amount of water and use a small amount of power. The cumulative effect of all this movement creates a vast increase in pressure and activates the large piston. In this case, several actuators act in concert to create the power source used by a large piston actuator.