Pressure vessels that store hydraulic energy when needed. In hydro-pneumatic accumulators, the compressibility of gas (nitrogen) is used to store pressurized fluid.
A proportional valve, also referred to as an electro-proportional valve produces an output (direction, pressure, or flow) proportional to an electronic control input.
These are fundamental components of any hydraulic or pneumatic system. Other terms used to describe them are bang-bang or discreet valves.
Manifolds are primarily used in hydraulic and pneumatic fluid power systems to control the flow of pressurized oil or air through circuits that power machinery.