05-11-2009, 02:29 PM
Hydraulic elevator systems lift weights using a hydraulic ram, a fluid-driven piston mounted inside a cylinder. The cylinder is connected to a fluid-pumping system (typically, hydraulic systems like use oil, but other incompressible fluids would also work). The hydraulic system has three parts:
A tank (the fluid reservoir)
A pump, powered by an electric motor
A valve between the cylinder and the reservoir
The pump forces fluid from the tank into a pipe leading to the cylinder. When the valve is opened, the pressurized fluid will take the path of least resistance and return to the fluid reservoir