Load-responsive steering control valve

A power steering system, comprising:

• a source of fluid pressure;
• a sump;
• first and second extensible and retractable hydraulic actuators;
• a manually operable main steering control valve;
• a supply conduit connected between the source and the valve, a drain conduit connected between the valve and the sump;
• first and second supply return lines respectively connected between the valve and respective first ends of the actuators, said valve being shiftable from a neutral position, wherein it blocks flow to and from the actuators, to a left-steer position wherein it connects the source to the first end of the first actuator while connecting a first end of the second actuator to the sump, and to a right-steer position wherein it connects the source to the first end of the second actuator while connecting the first end of the first actuator to the sump;
• a load-responsive valve means;
• said first and second supply-return conduits being connected to said load-responsive valve means;
• third and fourth supply-return conduits connected between the load-responsive valve means and the respective second ends of the first and second actuators;
• said drain conduit being connected to the load-responsive valve means;
• said load-responsive valve means including a first one-way valve connected to permit flow from the third supply-return conduit to the second supply-return conduit and a second one-way valve connected to permit flow from the fourth supply-return conduit to the first supply-return conduit;
• said load-responsive valve means including a pressure shiftable element means connected for sensing the pressure existing in the first ends of the actuators and operating, when the main steering control valve is in its right-steer position and the pressure in the first supply-return conduit is below and above a predetermined value, to respectively connect the fourth supply-return conduit to the drain conduit and to the first supply-return conduit and operating when the main steering control valve is in its left-steer position and the pressure in the second supply-return conduit is below and above the predetermined value, to respectively connect the third supply-return conduit to the drain conduit and to the second supply-return conduit.