Pressure sensing regenerative hydraulic system

A regenerative hydraulic system comprising

• a source of fluid pressure;
• a hydraulic actuator including axially reciprocating piston means disposed therein;
• a pressure sensing valve connected with said pressure source and actuator for fluid communication therebetween, said valve comprising;
• a housing having a longitudinal bore therein;
• a plurality of ports in fluid communication with said bore at spaced points therealong;
• valve plunger means disposed within said bore for slidable displacement between first and second positions to selectively interconnect a first pair of said ports for fluid communication therebetween in said first position and a second pair of said ports for fluid communication therebetween in said second position;
• biasing means urging said plunger means towards said first position;
• first and second pilot pistons slidably disposed in first and second pilot bores respectively, said first pilot piston of a diameter substantially smaller than that of said second pilot piston, said pilot bores being disposed substantially coaxially with said longitudinal bore, said second pilot bore communicating with said longitudinal bore through said first pilot bore wherein one end of said first pilot piston abuts one end of said second pilot piston and the other end of said first pilot piston abuts one end of said plunger means while in said first position, said first pilot piston having at least one flat means partially therealong to establish fluid communication between said second pilot bore and said longitudinal bore after said first pilot piston has been axially displaced a predetermined increment of distance while urging said valve plunger means from said first position to said second position;
• a first fluid path interconnecting one of said ports with said second pilot bore for transmitting fluid pressure to simultaneously urge the first pilot piston against said plunger means and the second pilot piston away from said plunger means;
• and
• a second fluid path interconnecting another of said ports with said second pilot bore for transmitting fluid pressure to urge the second pilot piston against the first pilot piston.