How a Hydraulic Cylinder Works
Most of us are familiar with equipment that is operated by hydraulics, but few of us know much about the hydraulic cylinder, one of the key components of this equipment. Of all methods of producing power, the hydraulic cylinder is probably the most efficient and compact. This may explain why hydraulics is the method most often used to produce linear motion that creates great power. But you can, if you wish, learn more about these cylinders and this linear motion that produces and transfers power.
The components of the cylinder that make up the entire mechanism are contained in a cylinder barrel. The micro-smooth inner walls of this barrel are machined to create this ultra smooth surface. Each end of this barrel is closed off and sealed, but at one of these ends you will find a sealed opening through which a piston rod moves into and out of the cylinder. This cylinder transfers linear the motion of the rod to some type of equipment such as a dump truck bed, bulldozer blade, airplane, elevator, and even the movement of some robots. Hydraulic fluid pumped into the hydraulic barrel creates the pressure that eventually results in a transfer of power that operates hydraulic equipment.
The principle used by a hydraulic cylinder to operate machinery is simply a transmission of force applied by pressure onto a fluid that is incompressible. Using the example of a dump truck and how it is operated using this hydraulic power, bed of the truck is raised when fluid is pumped into and out of a hydraulic barrel, depending on which way the truck bed moves. A control valve determines the flow direction either from a flow tank into the cylinder when the truck bed is raised, or from the cylinder back into the flow tank when the bed is lowered.
Fluid is a key part of the hydraulic cylinders ability to transmit power from one point to another. It can only transmit power if the fluid is incompressible. Otherwise, the fluid—which is usually a type of oil—would absorb a portion of the power, or energy, rather than transmitting it.
In a hydraulic system, the hydraulic fluid is always pumped, or transmitted, through a pipe from the point at which it receives the force, or energy, to the point where the energy is transferred to another piece of equipment that is to be moved or operated. This pipe can be any size or length without reducing or varying the energy it transfers. It can also be any shape and can be bent or straight. The pipe can also fork into two or more other pipes each operating a different and independent movement or operation.
One unique aspect of the hydraulic system is its capability to multiply power. It increases power in much the same way as a set of gears or a block and tackle. The principle is one that increases distance to produce more power. In hydraulics you create that same power increase by changing the size of the hydraulic cylinder.