This single-acting cylinder only has a head-end port and is operated hydraulically in one direction. When oil is pumped into a port, it pushes on a plunger, causing it to extend.
The return or retraction is effected by draining the hydraulic oil back into a reservoir. The plunger will fall, or return, because of the weight of a load or else induced by an additional mechanical force such as a spring.
The Double-Acting Cylinder must have ports at both the head and rod ends. The piston is moved by pumping oil into the head which moves the piston to extend a rod. Any oil in the rod end is pushed out into a reservoir. To retract the rod, the oil flow at both ends is reversed.
A nondifferential cylinder has a piston rod extending from each end. Thrust and speed are equal in both directions, provided that pressure and flow are stable.
This type of cylinder is not usually used on mobile equipment.
A telescoping, ram-type, actuating cylinder can be a single, or double-acting type. The construction of this cylinder is a series of rams are nested in a telescoping assembly.
With the the exception of the smallest ram, each ram is hollow and serves as a cylinder housing in its own for the next smaller ram contained within it. A ram assembly is contained in a main cylinder housing, which also provides the fluid ports.
This type of cylinder requires a small space with all of the rams retracted, but the telescoping action of the unit means that a relatively long stroke can be achieved when the rams are extended.
With a balanced, double-acting, piston-type cylinder, the working area on both sides of a piston is the same, and so the same force is exerted in both directions.
The cushioned cylinder is designed to slow an action and prevent shock loading at the end of a piston stroke. This cushion effect is created by building a limiting or metering device into the cylinder to restrict the flow at the outlet port which slows down the motion of the piston.
The single acting, spring loaded type cylinder is often called a piston type cylinder and is mostly used when push and pull functions are required.
This design of cylinder uses fluid pressure to apply force in one direction only, with the return force being applied with a spring.
The figure shows the spring being employed around the piston rod. However in some designs this can be reversed with the fluid on the piston rod side and the spring on the blank side.
For low pressure applications and where the cylinder is mounted vertically, the weight of the piston can be used instead of a spring.