The most common types of Cylinder assembly used in excavators are:
Single-acting cylinders
These cylinders provide power in only one direction. They are extended by hydraulic pressure and retracted by springs. Single-acting cylinders are commonly used for boom lift and bucket curl functions where the weight of the boom and bucket can retract the cylinder. They are simpler and more cost-effective than double-acting cylinders.
Double-acting cylinders
These cylinders provide power in both extension and retraction strokes. They use hydraulic pressure to both extend and retract the cylinder. Double-acting cylinders are commonly used for swing, boom extension, and outrigger functions where controlled power is needed in both directions.
Rod cylinders
These cylinders have a piston rod that extends out of one end of the cylinder barrel. They provide an openly exposed rod for connecting to linkages. Rod cylinders are commonly used for boom lift, bucket curl, swing and outrigger functions.
Telescopic cylinders
These cylinders have nested stages of barrels and rods that extend further than a single rod and barrel. They provide a very long stroke in a relatively compact cylinder. Telescopic cylinders are commonly used for boom extension to significantly increase reach.
Rotary actuators
These provide a rotational or turning force. They are commonly used to rotate the upper swing bearing of the excavator to provide swing function. Rotary actuators can rotate up to 360 degrees continuously.
Pivot cylinders
These cylinders have trunnion mounts on both ends to provide a pivot point. They are commonly used on excavator linkages and outriggers where a pivot point is needed. Pivot cylinders can push and pull through an arc.
The major types of cylinders used in excavators are single and double-acting cylinders to provide linear force, telescopic cylinders for long reach, rod cylinders for exposed stroke, rotary actuators for swing, and pivot cylinders where pivoting action is needed. These various cylinders work together to provide all the powered movements of an excavator.