Patent ID: 8893818

Claim:
A machine, comprising: first and second undercarriage assemblies; an engine supported by the first and second undercarriage assemblies and configured to drive associated tracks; a blade; a first push arm connected between the first undercarriage assembly and a first side of the blade; a second push arm connected between the second undercarriage assembly and a second side of the blade; a tank configured to hold a supply of fluid; a primary pump driven by the engine to draw fluid from the tank and pressurize a main flow of fluid; a pilot pump driven by the engine to draw fluid from the tank and pressurize a pilot flow of fluid; a first cylinder operatively connected between the first side of the blade and the first push arm; a second cylinder operatively connected between the second side of the blade and the second push arm; a first main spool movable between a first position at which the main flow of fluid is directed to a head-end of the first cylinder and fluid from a rod-end of the first cylinder is directed to the tank, a second position at which the main flow of fluid is directed to the rod-end of the first cylinder and fluid from the head-end of the first cylinder is directed to the tank, and a third position at which fluid flow through the first main spool is inhibited; a first pair of solenoid-operated valves selectively activated to direct the pilot flow of fluid to move the first main spool; a second main spool movable between a first position at which the main flow of fluid is directed to a head-end of the second cylinder and fluid from a rod-end of the second cylinder is directed to the tank, a second position at which the main flow of fluid is directed to the rod-end of the second cylinder and fluid from the head-end of the second cylinder is directed to the tank, and a third position at which fluid flow through the second main spool is inhibited; and a second pair of solenoid-operated valves selectively activated to direct the pilot flow of fluid to move the second main spool independently of the first main spool.