Steering control unit with low null band load sensing boost

A fluid controller operable to control the flow of fluid from a source of pressurized fluid to a fluid pressure operated device, the source of fluid including pressure responsive means for varying delivery of fluid to said controller in response to changes in a static load signal;

• said controller including housing means defining an inlet port for connection to the source of fluid, a control fluid port for connection to the fluid pressure operated device, a fluid return port for connection to a reservoir, and a load signal port for connection to said pressure responsive means;
• valve means disposed in said housing means and defining a neutral position, and an operating position providing fluid communication from said inlet port to said control fluid port;
• said pressure responsive means for varying delivery of fluid being selected to provide a predetermined standby pressure of the source of pressurized fluid;
• and said valve means defining a variable load sense drain orifice communicating from said load signal port to said fluid return port, said load sense drain orifice having a maximum flow area when said valve means is in said neutral position, and a decreasing flow area as said valve means is displaced from said neutral position toward said operating position;
• characterized by:
• (a) said valve means defining a variable load sense boost orifice communicating from said inlet port to said load signal port;
• and
• (b) said load sense drain orifice being sized, relative to said load sense boost orifice, to generate said static load signal to have a predetermined relationship to said predetermined standby pressure of the source of pressurized fluid.