Hydraulic control system having poppet and spool type valves

A hydraulic control system for controlling actuation of a hydraulic motor having first and second actuating chambers comprising:

• a control lever having a neutral position and movable in opposite directions therefrom;
• means for outputting a command signal corresponding to the direction and degree of movement of the handle from the neutral position;
• control means for processing the command signal and for producing and outputting first, second and third discrete control signals on the basis of the command signal;
• a spool type control valve having an inlet port, a tank port, first and second motor ports, and an elongate valve spool, the control valve having a neutral position at which the motor ports communicate with the tank port and the inlet port is blocked from the tank and motor ports, the valve spool being movable in a first direction to communicate the inlet port with the first motor port and a second direction to communicate the inlet port with the second motor port, the control valve being connected to the control means for receiving the first control signal and the valve spool being moved in the appropriate direction a distance proportional to the first control signal;
• a variable displacement pump connected to the inlet port of the control valve and having a displacement control means for receiving the second control signal and controlling the displacement of the pump in proportion to the second control signal;
• and
• a flow amplifying remotely controlled poppet type valve serially disposed between the first motor port and one of the actuating chambers in a manner to controllably meter fluid flow from the one actuating chamber to the first motor port when the third control signal is directed thereto and to normally block fluid flow from the one actuating chamber to the first motor port in the absence of the third control signal thereto, the poppet type valve being moved to an open position establishing substantially unrestricted fluid flow therethrough in response to fluid flow from the first motor port to the one actuating chamber.