single-acting cylinders

SINGLE-ACTING CYLINDERS

1. What are Single-Acting Cylinders?

• As the name suggests, single-acting cylinders can deliver a force in only one direction. 

• The single-acting cylinder is the simplest type of all hydraulic cylinders.

2. Construction

Single-acting cylinder has only one port at one end of the cylinder barrel to allow the hydraulic fluid. The schematic representation of a single-acting cylinder is depicted in Fig.5.1(a). Fig.5.1(b) show its symbolic representation. It is designed in such a way that the extending movement is forced by hydraulic fluid and the piston is retracted by gravity or a compression spring.

The piston is assembled inside a cylindrical housing called barrel. To maintain the close fitting between the piston and barrel, piston seal is attached at the circumference of the piston. A rod is connected to the piston and extended out of the barrel to deliver the force. At the other end of the barrel, there is a port for the fluid.

3. Operation

During the extending action, the force is applied by the pressurized fluid. The force applied to a piston depends on both the area of the piston and the pressure of the fluid. Mathematically, the force applied is given by

In single-acting cylinders, pistons do not retract hydraulically. But the retraction is accomplished by using gravity or by using the compression spring as shown in Fig.5.1 (a). If a cylinder is employed to lift a load, then the load itself can retract the piston.

4. Advantages and Disadvantages of Single-Acting Cylinders

• Advantages: The single-acting cylinders are very simple to operate, and compact in size.

• Disadvantages: The single-acting cylinders with spring return cannot be used for larger stroke lengths.