Hydraulic Cylinders | Design | Working | Types

Hydraulic Cylinders | Design | Working | Types

A hydraulic cylinder, which is also known as a linear hydraulic motor is a mechanical actuator (which means it helps a machine or a device in its operation) that is used to give a force which is basically unidirectional through a unidirectional stroke.

In other words, it can also be said that a hydraulic cylinder is used for the conversion of energy stored in the hydraulic fluid into a force that is used to create the movement of the cylinder in a linear direction.

It has a lot of uses, notably in construction equipment such as in engineering vehicles, machinery used for manufacturing, and civil engineering.

Design And Working Of Hydraulic Cylinder

The working principle of the hydraulic cylinder is Pascal’s law which simply says that in a fluid at rest in some container which is closed, a  change in pressure in one part is transmitted without any loss to every portion of the fluid and even to the walls of the container.

Larger the size of the cylinder, greater will be the force generated. The diameter of the piston is called the bore. A piston is situated inside the cylinder for some pushing fluids. So, if seen from the perspective of Pascal’s principle, larger bore cylinders will obviously have a higher capacity of lifting.

Source: www.hydraulicspneumatics.com

 

Hydraulic cylinder design typically consists of two cylinders having different diameters which are connected parallel to a pipe. The cylinders have two separate ports for the intake and the removal of fluid. This assembly is then filled partially using a suitable hydraulic oil which is not compressible.

A piston appears as a flat solid disk that has a rod attached to its center. While the force is applied to the smaller piston, it will try to compress the fluid present in the smaller cylinder. This will lead to the flow of fluid from a smaller cylinder to the larger cylinder through the tube connected and then the piston of the larger cylinder will move towards up due to this generated force.

The key factor that makes the piston move is the pressure difference generated inside the cylinder. When a  continuous pressure is applied and the cylinder reaches its maximum space, the pressure release valve will relieve the pressure generated and will make it possible to move further.

Classification Of Hydraulic Cylinders

1. According To Function

  • Single Acting Cylinders:

In single-acting cylinders, the fluid receives pressure from one side of the cylinder only, even during both the expansion as well as the retraction process. A spring or an external load is used in order to return the cylinder top to its original position which is referred to as the position when the pressure of the fluid is cut off.

Source: www.parker.com

 

  • Double Acting Cylinders

In the double-acting cylinders, the fluid is pressurized from both directions. Single cylinders containing springs are not used in large stroke applications since they consist of some inherent mechanical problems associated with the spring. The double-acting rods could be of two types:

  • Single rod ended
  • Double rod ended
Image result for double acting hydraulic cylinder design
Source: www.researchgate.net

2. According To Specifications

  • Plunger Cylinders:

Plunger cylinders are also named as Ram cylinders. These types of hydraulic cylinders are usually placed in an upright position. This is done as once the supply of the fluid gets stopped, the weight on the cylinder will make it return to its original position. The cylinders which are used in automobile service centers are a nice example of the plunger cylinders.

Image result for plunger hydraulic cylinder
Source: sc01.alicdn.com
  • Telescoping Cylinders

Telescopic cylinders usually have a maximum of six stages and are especially used in applications that have less area. Telescopic cylinders could either be single-action cylinders or double action ones. These cylinders often have a long stroke and are very helpful in some applications such as cranes and forklifts, etc.

Image result for telescoping hydraulic cylinder
Source: www.southhydcyl.com
  • Cable Cylinders

The cable cylinders could either be hydraulic or even pneumatic powered cylinders that are typical of the double-acting type. The strokes of these cylinders are mainly long and they produce moderate force. The cable cylinders are operated only in limited space.

  • Diaphragm Cylinders

Image result for diaphragm hydraulic cylinders
Source: www.ortegoglobal.com

 

Diaphragm cylinders are of two kinds- flat diaphragm cylinders and rolling diaphragm cylinders. These cylinders have zero leakage around the piston area.

Advantages Of Hydraulic Cylinders:

  • Due to the combination of hydraulic oil and servo valves, hydraulic cylinders can repeatedly hit targets within a small range. So, they are very accurate or precise.
  • The speed of hydraulic cylinders is independent of the mechanisms of operation, so it is not affected by the weight of the load like the electronic systems.
  • Hydraulic cylinders can produce a very large amount of force despite their small size. So, the user does not need to worry about any kind of support.
  • Little power is required to operate the mechanisms used by hydraulic cylinders which is helpful in conserving energy and saving money.
  • Hydraulic cylinders are really very reliable, even when the weather is harsh.

Disadvantages Of Hydraulic Cylinders:

  • Efficiency of a hydraulic cylinder is a little bit lower than efficiency of mechanical and electric transfers, and during the regulation process, it is reduced further.
  • Conditions of operation of a hydraulic cylinder such as temperature have a great influence on its characteristics.
  • Efficiency of a hydraulic cylinder is reduced a little in the process of exhaustion of its resource mainly due to the increase in backlashes and the increase of outflow of the liquid

Conclusion:

After reading this article, we can say that hydraulic cylinders offer versatility and higher power density as compared to other systems. They consist of fewer components than other cylinder systems.

Hope this article helps!

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