Hydraulics is a technique by which signals, power or energy are transmitted using fluids. 

Hydraulics was “invented” by the Englishman Joseph Bramah, one of the most important engineers of the Industrial Revolution. As early as 1795, he developed a hydromechanical machine that worked according to the hydrostatic law formulated by Blaise Pascal and was operated with pressurized water.

This machine was able to increase the force applied by a factor of 2034. 

Blaise Pascal
Joseph Bramah
William G. Armstrong
Reynold Janney

In 1851, William Arstrong developed an accumulator that could generate large volume flows, the so-called weight accumulator. 

In 1905, mineral oil was used for the first time as a transmission medium in a hydrostatic transmission of axial piston design, developed by Reynold Janney and Harvey Williams. Until today oil remains the primary transmission medium in hydraulic systems. 

Although hydraulics have certain disadvantages, primarily the risk of leakage combined with the escape of environmentally harmful oil, the technology is still the medium of choice in many areas. 

Enormously large forces and torques can be generated in a simple manner. Since the pressure of the hydraulic unit is permanently applied during operation, it can be called up much more quickly than, for example, with a servomotor, which first has to build up the force.

At the point of use, the hydraulic system is very space-saving, since the separated design of input and output means, that the hydraulic power unit can be located in a place with sufficient space. 

Hydraulic Power Unit by Bosch Rexroth
Hydraulic Cylinder

A more recent branch of hydraulics is micro-hydraulics. Even though the term is common, there is no definition or even standardization. In general, it is understood to mean hydraulic components with a nominal diameter of up to 3mm and volume flows of up to approx. 20L/min. Pressures of up to 300bar can be achieved. 

Microhydraulics are often designed as a closed system, minimizing the risk of leakage. Even in the event of a leak, the amount of oil used is extremely small, so there is no risk of major environmental damage. 

Micro-hydraulics are used in a wide range of applications, including medical technology, lifting platforms, hand tools, rescue robots, the aircraft industry and the automotive sector.

Micro-Hydraulic Components