quote from SUN document.. "Regenerative circuits allow a cylinder to be advanced more rapidly than it could be with pump flow alone. To achieve this, oil from the rod end of a cylinder is added to the pump flow to the blind end, increasing the rate of advance.
NOTE: Regeneration circuits apply only to single rod cylinders in the extended direction."
When a force from gravity or inertia extends the cylinder, the rod side might drain faster than the pump can fill the void on the capped side, and capped side will be subject to cavitation. By linking the flow from the rod side over to the capped side, pump only need to fill the volume difference, which is equal to the volume of the piston rod.
Such flow link system is called regeneration of flow.
There are a few ways to regenerate flow, the control valve spool can be designed to be regenerative, and there are inline valves (SUN valves), that can regenerate flow.
