The VVR's flexible bellows is key to the concept

It allows expansion and contraction to take place as fluid thermal temperature changes.

VVR retracted (empty)
VVR extended (full)

The bellows also reacts to differential volumes caused by cylinder rod motion. Thus the cylinder rod volume only must be taken into account in the reservoir size requirement additionally to the network fluid volume expansion. The VVR is not affected or dependant of pump flow since the network main return line is directly routed to the pump inlet where the VVR installed near the pump will only see differential volume.

The VVR is sealed, airless and slightly pressurized (1 to 9PSI / 0,1 to 0,6bar) thus supercharging the pump inlet no matter the operating altitude and machine orientation. One VVR can feed many pumps or one per pump to isolate circuits. Many VVR's can be installed in series or parallel to increase volume.

Operating principle

Motor video and animation

This representation shows the VVR thermal compensation from temperature changes regardless of motor size: flow IN = flow OUT.

Cylinder video and animation

This representation shows the single rod cylinder differential volume compensation from the VVR.
ONLY the total differential volume of all cylinders rods that can be activated at the same time must be considered when calculating the differential volume requirement.

General presentation

VVR-800 on test-stand - activation of a cylinder with 587 cubic inches (2.5 gal or 9.6 liters) of differential volume

Patented design → US #6,772,794 B2 / #6,981,523 / Canada #2,464,829