Hydraulic valve means

A hydraulic system for controlling a hydraulic motor as to speed as well as to direction of movement, said motor having motor ports serving alternatingly as an inlet for receiving a medium and as an outlet for returning the medium, said hydraulic system comprising:

• a tank for containing a supply of the medium;
• a main supply flow passage for delivering the medium to said inlet port;
• a return flow passage for returning medium from said outlet port to said tank;
• a pump connected to said tank for delivering pressurized medium to said main supply flow passage;
• and
• a plurality of valve means for controllably opening and closing said main supply flow passage and said return flow passage to control the movement direction of the motor, said plurality of valve means including:
• an inlet seat valve for each motor port located in said main supply flow passage between said pump and said motor port and an outlet seat valve for each motor port located in said return flow passage between said motor port and said tank, wherein said inlet and outlet seat valves each comprise a housing and a valve body movable within said housing from a closed position to an opened position and being pilot operable independent of the pressure by a pilot flow through a variable flow restriction channel in each valve body for conveying said pressure medium to a pilot flow chamber in the housing of each seat valve to any position between said closed and said opened positions to control the amount of the pressure medium flowing through the main supply flow passage to the inlet motor port and of the pressure medium flowing through the return flow passage to the tank, respectively, and a pilot valve for each one of the inlet and outlet seat valves to obtain and control said pilot flow through said seat valves, wherein each pilot valve associated with the inlet seat valve for controlling the position of the valve body thereof independent of the pressure in the main supply flow passage comprising a housing having a pilot valve channel with a pilot inlet and a pilot outlet, means for selectively opening and closing said pilot valve channel, a first inlet pilot valve passage communicating said pilot inlet with said pilot chamber of the inlet seat valve and a first outlet pilot valve passage communicating said pilot outlet with said main supply flow passage at a location downstream of said inlet seat valve, and wherein each pilot valve associated with said outlet seat valve for controlling the position of the valve body thereof independent of the pressure in the return flow passage comprising a housing having a pilot valve channel with a pilot inlet and a pilot outlet, means for selectively opening and closing said pilot valve channel, a second inlet pilot valve passage communicating said pilot inlet with said pilot flow chamber of the outlet seat valve and a second outlet pilot flow passage communicating said pilot outlet with said return flow passage at a location downstream of said outlet seat valve.