Ratio valve to control unloading of modulating relief valve

A valve assembly adapted for use in a fluid system, comprising:

• a housing defining a single bore, an inlet port, a control port and a plurality of drain ports each intersecting the single bore in axially spaced relation;
• a load piston slidably disposed in the single bore;
• a valving element slidably disposed in the single bore adjacent the load piston and movable between a first position at which the inlet port is blocked from one of the plurality of drain ports and a second position at which the inlet port is open to the one drain port, said valving element defining a blind bore in one end and an annular groove in the outer periphery thereof, a passage is defined in the valving element interconnecting the blind bore in the valving element with the annular groove thereof and another one of the plurality of drain ports, and another passage is defined in the valve element interconnecting the blind bore in the valving element and the control port in the housing;
• a pressure chamber defined in the single bore between the load piston and the valving element;
• a ratio valve mechanism slidably disposed in the blind bore of the valving element and movable between a first position at which the first mentioned passage in the valving element is blocked from the pressure chamber and a second position at which the first passage is open to the pressure chamber, said ratio valve mechanism defining a predetermined effective cross-sectional area in communication with the pressure chamber and a smaller effective cross-sectional area in continuous open communication with the control port through the another passage in the valving element.