Variable load valve device having adjustable bias means to withhold proportional brake control during low level brake requirements

For a vehicle having load-dependent fluid pressure cushion means supporting the vehicle, there is provided a variable load valve device for automatically developing brake pressure in accordance with the vehicle load condition comprising:

• (a) an inlet and an outlet via which the vehicle brake pressure is transmitted;
• (b) a control chamber to which said inlet is connected;
• (c) a delivery chamber to which said outlet is connected, said control and delivery chambers being interconnected to provide the fluid pressure transmission between said inlet and outlet;
• (d) a first piston subject to said control chamber fluid pressure for movement in one direction;
• (e) a second piston subject to said delivery chamber fluid pressure for movement in a direction opposite said one direction;
• (f) means for interconnecting said first and second pistons to provide mechanical advantage therebetween;
• (g) valve means operative responsive to movement of said first and second pistons in said one direction to establish fluid pressure communication between said control and delivery chambers, and operative responsive to movement of said first and second pistons in said opposite direction to interrupt fluid pressure communication between said control and delivery chambers;
• (h) load responsive means subject to the fluid pressure of said cushion means for varying the mechanical advantage of said interconnecting means;
• wherein the improvement comprises:
• (i) means acting on said interconnecting means for biasing one of said first and second pistons in said one direction.