Glossary · Pneumatics and hydraulics
Single-acting cylinder
Also known as: Spring-return cylinder
German: Einfachwirkender Zylinder
In fluid power, a single-acting cylinder is a cylinder in which fluid pressure acts on one side of the piston only, producing force in one direction, while the return stroke is made by a spring, gravity or external force.
- Fluid power
In one sentence
A single-acting cylinder is powered in one direction only; a spring, gravity or external force makes the return stroke.
Example
A clamping cylinder is single-acting with spring return, so it opens automatically when air is exhausted.
How it applies
- Engineering: Single-acting cylinders need only one air connection and a simpler valve, and they move to a defined position on air loss. The spring reduces available force and limits stroke.
- Commissioning: Check that the return force is sufficient under all load conditions.
- Maintenance: The internal spring is preloaded; disassembly can release it suddenly.
- Documentation: Describe the position the cylinder takes on air loss and whether that is safe in each operating state. Warn about the preloaded spring as Stored energy during disassembly.
Single-acting vs. double-acting cylinder
A single-acting cylinder has a powered stroke and an unpowered return. A Double-acting cylinder is powered both ways and has no spring-defined rest position.
In the circuit diagram, the spring is part of the symbol; refer to it in the text when explaining rest positions.