Telescopic Hydraulic Cylinder Working Principle

What is telescopic hydraulic cylinder

Telescopic hydraulic cylinder, we also call it as multi stage hydraulic cylinder or combined hydraulic cylinder. It is a kind of special hydraulic cylinder with a wide range of applications. According to the number of telescopic stages, it can be divided into 2, 3, 4, and 5 stage telescopic hydraulic cylinder. According to the number of times of liquid supply to complete a working cycle, there are single acting and double acting multi stage hydraulic cylinders. Among them, the single acting multi stage cylinder is a plunger telescopic hydraulic cylinder. The double acting multi stage hydraulic cylinder is a piston type telescopic hydraulic cylinder. There is also a telescopic hydraulic cylinder in which the last stage is a piston, and the previous stages or one stage are plungers.

Structure

Piston type double acting two stage telescopic hydraulic cylinder, the first stage piston assembly includes a piston seal ring, the outer wall of the piston rod of the first-stage cylinder, and the inner wall of the first stage piston rod. The secondary piston rod assembly includes a piston rod, a piston and a seal. At the same time, the inner wall of the primary piston rod is the secondary piston rod cylinder barrel, and the front end cover of the secondary piston cylinder with the guiding function is also a constituent part of the primary piston rod. Initially, the second stage small piston locates on the upper part of the first stage big piston, and the first stage big piston locates at the bottom of the telescopic tube. When pressure oil is supplied from the right port, the primary and secondary piston assemblies move upward at the same time.

The telescopic hydraulic cylinder contains two or more piston hydraulic cylinders. The piston rod of the previous stage piston cylinder is the cylinder barrel of the next stage piston cylinder.

The total stroke of the telescopic hydraulic cylinder is the sum of the strokes of the sleeves at all levels, so it can be quite long. When not working, the length of the entire hydraulic cylinder can be shortened very short. It is widely used in occasions where installation size requirements and large working stroke requirements are required. The most typical application example is the telescopic boom of a truck crane. In addition, it has also been widely used in the hydraulic supports of dump truck cleaning vehicles and mining machinery.

Working principle

When the pressure oil enters from the rodless cavity, the cylinder with the largest effective area of the piston begins to extend, and when it reaches the end, the cylinder with the second effective area of the piston begins to extend. The sequence of the telescopic hydraulic extension is from large to small, and obtains a long working stroke. The smaller the effective area of the extension cylinder, the faster the extension speed.

Therefore, the extension speed becomes slower and faster, and the corresponding hydraulic thrust changes from large to small. This change rule of thrust and speed is just suitable for the thrust and speed requirements of various automatic loading and unloading machinery. The order of retraction is generally from small to large, with a shorter axial length during retraction, which occupies a small space and has a compact structure. Application field is normally hydraulic systems of construction machinery and other mobile machinery, such as cranes and dump trucks.

The cylinders of different levels of the telescopic hydraulic cylinder increase gradually. When the load is constant, the working pressure increases gradually. When working, the first-stage hydraulic cylinder of the telescopic hydraulic cylinder stretches out first, and the last-stage cylinder stretches out last. When returning, the last hydraulic cylinder will return first, and the first hydraulic cylinder will return last.

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