A hydraulic cylinder turns the energy in pressurized fluid into straight-line motion. It does this by directing oil into a chamber where it pushes on a piston. The piston moves inside a barrel and carries a rod that connects to the machine. The cylinder’s force depends mainly on pressure and effective piston area; its speed depends mainly on flow and that area.
The main parts
The barrel contains the piston and fluid. The piston separates the barrel into two chambers. The rod transfers motion to a gate, boom, press ram or other load. A gland supports the rod as it exits the barrel. Piston and rod seals limit internal and external leakage, while a wiper helps keep outside dirt away from the rod seal. Ports connect the chambers to the hydraulic circuit. Mounting points transfer force into the machine structure.
What happens during extension and retraction?
In a common double-acting cylinder, oil entering the cap-end port acts on the full piston area and extends the rod. Oil from the opposite chamber returns to the tank through the control circuit. To retract, the valve reverses the flow: pressure enters the rod-end chamber and pushes on the smaller annular area around the rod. A single-acting cylinder uses hydraulic pressure in only one powered direction and needs a spring, gravity or an external load for return.
Why the hydraulic circuit matters
The pump supplies flow; the valve chooses direction; pressure develops when the load resists motion. The reservoir, filters and often a cooler support reliable operation. A cylinder cannot be selected only from a photograph because pressure, flow, load, mounting, stroke, fluid and temperature all affect the result. A holding function also depends on the valve arrangement and machine safety design, not merely the cylinder body.
What to remember
Pressure helps determine available force, flow helps determine speed, and geometry determines travel and mechanical fit. For an application, start with load cases and installation drawings, then specify the cylinder and circuit together. See Yongjian’s Hydraulikzylinder-Sortiment und contact the engineering team with a drawing for a specific review.
Technische Hinweise: Leitfaden zur Auswahl von Parker-Hydraulikzylindern. Die obige Erläuterung wurde unabhängig davon für allgemeine Informationszwecke verfasst; endgültige Auslegungswerte erfordern eine projektspezifische Prüfung.