In hydraulic-system architecture, component design is shaped by operational requirements. Although more hydraulic lines or complex control mechanisms are often associated with higher performance, genuine success in industrial design lies in achieving maximum reliability with the minimum number of components. Single-acting telescopic cylinders are among the clearest examples of this simple and functional design philosophy. HMLIFT’s nearly half-century of production and design experience demonstrates the high engineering standard underlying this apparent simplicity.

Operating Principle of a Single-Acting System

Single-acting telescopic cylinders integrate basic physical principles and gravity into the system. Hydraulic power is used actively in only one direction—during cylinder extension and body lifting. No external hydraulic force is required for the return movement; the body’s own weight and gravity close the system.

The cycle operates as follows:

• Lifting Stage: Pressurised hydraulic oil generated by the pump is delivered to the cylinder through a single line. The volumetric force of the oil extends the stages sequentially and raises the body.
• Lowering Stage: The directional control valve shifts and opens the return path from the cylinder to the tank. The body’s weight pushes the stages inward, oil returns to the tank and the cylinder retracts to its compact form.

This design eliminates the need for a second hydraulic line, complex double-direction valves and additional energy to pull the body downward.

Structural Components and Material Technology

Stable performance of a single-acting telescopic cylinder in demanding field conditions depends on the quality of the materials and the precision of manufacturing tolerances.

ST 52 Cold-Drawn Tube Technology

Cylinder bodies are manufactured from cold-drawn tubes conforming to ST 52 standards. Compared with hot rolling, cold drawing provides much tighter dimensional tolerances and a higher-quality internal surface. Tight tolerances preserve the axial accuracy of stage movement, while the smooth surface directly extends the service life of sealing elements.

Hard-Chrome Plating and Surface Resistance

The outer surfaces of the stages are hard-chrome plated to improve wear and corrosion resistance. Coating thickness, hardness and surface roughness are fundamental factors determining cylinder service life. In special series such as Diamond, the surface technology is further optimised to meet high-pressure standards.

Temperature Capability and Sealing

System sealing must retain mechanical stability under varying environmental conditions. HMLIFT telescopic cylinders operate as standard from -40°C to +80°C. Special sealing and material configurations are available for extreme winter conditions down to -40°C, such as those encountered in Russia and Northern Europe.

Broad Range of Configurations and Integration Options

The single-acting telescopic cylinder family can be configured for applications ranging from small agricultural equipment to large semi-trailer projects. First-stage diameters from 63 to 245 mm, two to ten stages and stroke alternatives exceeding eight metres—from 2,470 to 8,675 mm—demonstrate this flexibility. Six connection types, A, B, C, E, H and K, are available to match different mounting geometries.

A complete spare-parts ecosystem, ranging from seal kits and wire retaining-ring sets to brackets and cradle systems, also supports long-term operational continuity.

Conclusion

The functional simplicity of single-acting telescopic cylinders confirms a fundamental engineering principle: the most effective solutions are those free from unnecessary complexity. Combined with correct material selection, precise tolerance management and broad climate capability, these designs provide a strong foundation for long-term reliability in industrial vehicle-mounted applications.