A hydraulic cylinder is a mechanical device for the transfer of energy through the use of high-pressure oil, acting against the surface area of the piston inside the cylinder.
A hydraulic cylinder provides linear force on one axis in one or two directions (known as a cylinder with one or two cylinders, respectively).
A cylinder usually consists of 4 or 5 components:
- Pipe
- Piston (optional)
- Rod
- Greasiness
- End cap
In a typical hydraulic cylinder with piston oil, it is fed at both ends through any type of port, and the piston is sealed into the tube using a double-acting seal, as well as between the stem and the gland using a single-sided seal. In addition, you will usually find that the wiper seal is used in the gland to keep dirt out. This illustration is known as a double acting cylinder.
This pressure acts on the surface of the piston, which causes the hydraulic cylinder to create a linear movement. Since the rod is fixed on the piston, it also moves. Applying hydraulic pressure through the port to one side of the piston causes it to move in one direction, and applying pressure through the port to the opposite side of the piston will cause it to move in the opposite direction.
In a cylinder with one action, the oil acts only on one side of the piston; therefore, it can only be mechanically moved in one direction. An external force (gravity, or sometimes a spring or other hydraulic cylinder) provides the force in the opposite direction.
Cylinders with one action can also be of the “displacement” type, where the oil pressure acts directly on the end of the rod, and there is no piston. In this cylinder design, the force is limited by the surface area of the rod, while in a cylinder with a piston the rod can be of any size and the force can be calculated or controlled by the design of the piston.
Usually, one end of the tube is fixed, and an object to be moved is attached to the end of the rod, although it is possible to fix the end of the rod and attach an object that is moved to the end of the tube.
In a double-acting cylinder, the “closing” power is always less than the “open” power due to the reduced surface area of the oil piston. This reduced surface area is equal to the surface area of the rod end.
The size of a hydraulic cylinder can be almost limitless, usually from a few centimeters in length to a few meters, although theoretically there are few limitations.
