Hydraulic Cylinders – Types, Design and Working

Apparently a mechanical actuator, a hydraulic cylinder is mainly used for providing unidirectional force via unidirectional stroke. There are different types of hydraulic cylinders available in the market but the two primary cylinders are the tie rod cylinder and the welded body cylinder. Though, there are special cylinders also available which are namely the Telescopic cylinder, position sensing cylinder, differential cylinder and the plunger cylinder.  There are reciprocating engine cylinders also available and are classified into single acting and double acting cylinders on the basis of the action of the working fluid on the piston.

 

Cylinder design and components - Any basic cylinder is made up of cylinder base, cylinder barrel, piston, piston rod, seals and sea gland primarily while the other components include cushions, cylinder base connection, cylinder head caps, but plates, pivot pins, spherical ball bushings, alignment coupler and more. The hydraulic cylinder gets its power from pressurized fluid, namely oil. The built of a hydraulic cylinder includes a cylinder barrel which has a piston connected to piston rod that moves back and forth. One end of the barrel is closed by cylinder head and other end by cylinder bottom. The piston comes out of the cylinder at the cylinder head and has sliding rings as well as seals. It also has mounting attachments for the purpose of connecting the cylinder to the machine component or the object.

The motor side or the actuator of the system is hydraulic cylinder while the hydraulic pump is the generator

As mentioned before there are specials cylinder available also. Here is a run down the special cylinder.

Plunger cylinder – It is a hydraulic cylinder but it either has a piston without seals or is piston free. This cylinder can be used only as pushing cylinder and has a relatively thick piston.

Differential Cylinder – This cylinder also acts just like a normal hydraulic cylinder when it is pulled but when the cylinder is pushed the oil from the cylinder’s piston rod side flows to the cylinder’s bottom and is not returned to the reservoir. A differential cylinder can give a maximum force equal to that of a plunger cylinder but it goes much faster.

Telescopic cylinder -  Usually when the length of the connections does not fit in the cylinder, piston rod is used as the piston barrel and a second piston rod is used inside it. These type of cylinders are known as telescopic cylinders. These cylinders are multi-stage units which have stages from one to five and more also. Most telescopic cylinders are single acting cylinders and are highly expensive as compared to normal hydraulic cylinders.  The work mechanism of a single acting cylinder is that the working fluid is acting on either side of the piston only. For pushing the piston back in the other direction, it relies upon springs, loads, momentum of a fly wheel as well as other cylinders. Most reciprocating engines are said to be having single acting cylinders only. Single acting cylinders find their application in steam engines, stirling engines, external combustion engines, internal combustion engines, hydraulic rams and pumps.