Telescopic Cylinder
A telescopic cylinder produces a stroke several times its closed length using nested stages. On 3-5 stage types the extended length typically reaches 3-5 times the closed length. It is preferred on dump bodies and crane booms because of space constraints.
The stages extend in sequence: the stage with the largest area comes out first, because at the same pressure it produces the highest force. As the stages progress the area shrinks; at constant flow, speed increases and force drops. That is why you feel the motion getting faster and the power dropping as it rises.
- Force profile: highest push on the first stage, lowest on the last.
- Speed profile: the opposite; the last stage is the fastest extending section.
- Retraction order: the reverse of extension; the smallest stage retracts first.
When working with electronic lever control, this variable characteristic causes speed to change as stages shift even at a fixed joystick opening. A ramp time and a characteristic that is fine in the mid region and fast at the ends is useful here; the HCT402's parabolic joystick behavior exists precisely to make such variable-speed motions easy to manage.
Where this term is used: What Is a Hydraulic Lever Retrofit Kit? Definition, Components, Operating Principle