|
Hydraulic and Pneumatic Knowledge
Fluid Power Equipment | Hydraulic Actuators
Previous
Page
The hydraulic supply and return line is connected to the lower
chamber and allows hydraulic fluid to flow to and from the lower chamber of the
actuator. The stem transmits the motion of the piston to a valve.
Initially, with no hydraulic fluid pressure, the spring force
holds the valve in the closed position. As fluid enters the lower chamber,
pressure in the chamber increases. This pressure results in a force on the
bottom of the piston opposite to the force caused by the spring. When the
hydraulic force is greater than the spring force, the piston begins to move
upward, the spring compresses, and the valve begins to open. As the hydraulic
pressure increases, the valve continues to open. Conversely, as hydraulic oil is
drained from the cylinder, the hydraulic force becomes less than the spring
force, the piston moves downward, and the valve closes. By regulating amount of
oil supplied or drained from the actuator, the valve can be positioned between
fully open and fully closed.
The principles of operation of a hydraulic actuator are like
those of the pneumatic actuator. Each uses some motive force to overcome spring
force to move the valve. Also, hydraulic actuators can be designed to fail-open
or fail-closed to provide a fail-safe feature.
Previous
Page
© Copyright 2000 - 2009, by Engineers Edge, LLC All rights reserved.
Disclaimer
|
