Copyright Goodheart-Willcox Co., Inc.
126 Hydraulic Systems for Mobile Equipment
A single-acting cylinder could be designed so that fl uid pressure is used
only to retract a cylinder, and a weight is used to extend the cylinder. See
Figure 6-2. However, this arrangement is rarely found in mobile equipment.
This application is also an example of an overrunning load, which creates prob-
lems. Chapter 7 will discuss a pressure control valve that is used to resolve
problems with overrunning loads.
Figure 6-1. Single-acting cylinders. A—The most common single-acting cylinder application uses fluid pressure to
extend the cylinder and some type of external force to retract the cylinder. B—This single-acting cylinder is being
used on a combine simulator. Notice the cylinder only has one hydraulic hose, and a heavy weight is used to retract
the cylinder. The cylinder is emulating the header raise function. The cylinder could be used as a double-acting
cylinder, but a breather is installed in the other hydraulic port.
Weight
Breather
Cylinder
A
B