Telescopic Cylinders for Long Stroke Lengths

The hydraulic pressure intensification is a simple yet highly effective method for generating very high compression forces. However, a challenge arises when these high compression forces must also be applied over a long working stroke. Since standard hydraulic cylinders become very impractical beyond a certain length, telescopic cylinders were developed.

Design of a Telescopic Cylinder

A telescopic cylinder consists of multiple hydraulic cylinders nested within one another. Manufacturing a telescopic cylinder requires maximum precision. Maintaining the required tolerances for inner and outer diameters is essential.

The individual tubes are inserted into one another and sealed against each other by sealing rings. Telescopic cylinders typically employ multiple seals arranged in series to ensure maximum sealing against hydraulic pressure at all times. Technically, a telescopic cylinder therefore differs little from a standard hydraulic cylinder: When the telescopic cylinder is pressurized, the individual nested cylinders gradually extend apart. A stop at the base of each cylinder prevents the telescopic cylinder from separating during extension.

Applications of Telescopic Cylinders

Telescopic cylinders are used wherever limited installation space coincides with the need for long stroke lengths. A typical example is the lifting mechanism of a three-way tipper truck. Three-way tippers play a major role in transporting bulk construction materials. Gravel, sand, and aggregate must be unloaded at construction sites as the environment permits. The unloading options can therefore vary considerably. A three-way tipper truck meets this challenge with maximum flexibility. This type of truck faces the particular challenge of being able to tip a multi-ton loaded bed to both sides and to the rear. For this purpose, the bed hinges are designed to be interchangeable. However, the hydraulic cylinder in these commercial vehicles is typically designed as a telescopic cylinder. It ensures that the bed can be raised in any direction to an almost vertical position. This guarantees complete emptying of the bed and maximum versatility of the three-way tipper truck.

Sizes of Telescopic Cylinders

Theoretically, a telescopic cylinder can consist of any number of stages. In the retracted state, the cylinder always remains the same length—however, it also becomes increasingly wider. This can also become impractical sooner or later. Furthermore, the stability of the hydraulic system naturally suffers with the increase in stages and therefore seals. However, thanks to new manufacturing processes and improved materials, hydraulic cylinders with up to eight stages are now available. Even at this high level of complexity, the cylinders can still handle an internal pressure of 180 bar while developing a lifting force of 11 tons.

However, the difference from single-stage cylinders is clearly visible here: 180 bar is comparatively low for a hydraulic system. In construction engineering, pressures are used that can easily reach twice that amount. This makes the use of telescopic cylinders always a challenge that must be precisely calculated.

Space-Saving, Practical, and Powerful—Telescopic Cylinders for Special Applications

Telescopic cylinders are the logical evolution of single-stage hydraulic cylinders. They are technically more challenging but can also provide good lifting force in confined spaces. When not in use, they are very space-saving, thereby increasing the efficiency of the entire system.