A hydraulic cylinder converts hydraulic energy into linear mechanical energy. It is also called as linear actuator. The piston placed inside a cylinder can be made to move to a required distance at a required point of time by the liquid.
In order to maintain perfect alignment between piston and cylinder, a leak proof arrangement of piston ring and packings (cup shaped packing & ‘V’ shaped packing) are introduced between piston and the cylinder.
Cylinders are used to begin or stop any stroke movement or to clamp an object at a particular position.
There are different types of hydraulic cylinders namely
- Single acting cylinder
- Double acting cylinder (with one piston rod)
- Double acting cylinder (with two piston rods)
- Ram type cylinder
- Multi stage cylinder
- Telescopic cylinder
- Tandom or combination cylinder
In a single acting cylinder, the hydraulic liquid is allowed to pass through from only one side as shown in the diagram. The piston moves to the other side because of the pressure of the liquid.
On release of the pressure, the piston reaches its original position due to its own weight or by a spring arrangement.
In double acting cylinders, the liquid is allowed from both the ends alternatively. So the system is controlled effectively. There are two types in double acting cylinders – with one piston rod & two piston rods. In the two piston rods double acting cylinder, the speeds on both the directions are equal.
In a ram type cylinder, the piston and the piston rod is replaced by a ram of uniform diameter. They are used in presswork of large capacity. A multi stage cylinder is a device in which several cylinders are placed in linear arrangement.
Telescopic cylinders provide a compact arrangement when the cylinder needs to move by a longer distance. Two or more cylinders are arranged one inside the other and the central cylinder alone is provided with a piston. When objects of high mass are lifted for greater heights, vehicles with fork lifts are used. Such devices are fitted with this type of cylinders.