Chapter 2 Fluid Power Systems 39
to the piston and this assembly is located in the
chamber with the rod extending through one of
the end caps. The closed chamber is divided into
two parts by the piston. Ports are located in each
of the end caps. Appropriate seals are located
between the end caps and cylinder, piston and
cylinder, and piston rod and end cap.
Forcing fluid into the cylinder through a port
causes the piston rod to move out of the cylinder on
the extension stroke and back into the cylinder on
the retraction stroke. This produces linear motion
for use in a machine. Figure 2-9 shows a cylinder
used in the steering system of a lawn tractor.
Motors
Fluid power motors have many of the same
basic design characteristics as pumps. There are
several different motor designs, ranging from
simple to very complex. A basic motor consists of
a housing, rotating elements, power output shaft,
ports, and seals. The housing provides a closed
chamber to retain system fluid. The rotating ele-
ments divide the housing chamber into intake and
outlet sections. The power output shaft is attached
to the rotating elements. Ports are provided in both
the intake and outlet sections of the housing cham-
ber. Seals are provided to prevent leakage of fluid
between the housing and rotating elements and
between the housing and the power output shaft.
Forcing fluid into the motor causes the rotat-
ing elements to turn the power output shaft.This
produces rotary motion for use in a machine.
Figure 2-10 shows a fluid power motor in an agri-
cultural application.
Ports
Cylinder
end cap
Cylinder
end cap
(integral)
Piston
Piston
rod
Cylinder
body
Seals
Figure 2-8. A cross section of a fl uid power cylinder.
(Used with permission of CNH America LLC)
Cylinder
Figure 2-9. A typical fl uid power cylinder. This cylin-
der is used to assist the steering of a lawn tractor.
Figure 2-10. A typical fl uid power motor (red com-
ponent). The construction of motors and pumps is
similar. Several different designs are used in fl uid
power systems.