4. Return port
6. Pressure port
Figure 3-21.Typical relief valve.
Figure 3-19.Globe valve.
system are the poppet (fig. 3-25), rotary spool (fig.
3-26), and sliding spool valves (fig. 3-27).
Figure 3-20.Cross-sectional view of a needle valve.
An actuating cylinder is a device that converts
fluid power to linear motion, or straight-line force and
motion. Since linear motion is a back-and-forth motion
along a straight line, this type of actuator is sometimes
referred to as a reciprocating. The cylinder consists of a
ram or piston operating within a cylindrical bore.
Actuating cylinders may be installed so that the
cylinder is anchored to a stationary structure and the
ram or piston is attached to the mechanism to be
operated, or the piston or ram may be anchored to the
stationary structure and the cylinder attached to the
mechanism to be operated.
and piston are often used interchangeably. However, a
ram-type cylinder is usually considered one in which
the cross-sectional area of the piston is more than one
halfofthe cross-sectional area of the movable element.
In most actuating cylinders of this type, the rod and the