Control valve for pressure-medium servo-motor

A control valve for a pressure medium operated servo-motor of a servo-steering mechanism of the type having working pressure chamber means at respective oppositely directed working surfaces of relatively movable piston-cylinder means;

• said control valve comprising:
• valve housing means,
• valve adjusting means movably disposed in said valve housing means for controlling fluid pressure supply to said working pressure chamber means, said valve adjusting means being disposed to be acted upon by load dependent reaction pressure of said working chamber means in a direction opposite the direction of movement of said valve adjusting means from a neutral position,
• double action reaction piston means, said reaction piston means having two oppositely acting reaction relief pressure surface means,
• prestressed reaction spring means supporting said reaction piston means in both respective opposite axial directions with respect to said valve housing means,
• and reaction piston connecting means connecting said reaction piston means with limited movement with said valve adjusting means while enabling a limited free relative adjusting path between said valve adjusting means and said reaction piston means, wherein said reaction relief pressure surface means is acted on by said reaction pressure forcing said reaction piston means in a direction reducing the effect of said reaction pressure on said valve adjusting means, whereby increase of said reaction pressure above a predetermined value results in movement of said reaction piston means against said reaction spring means to engage said connecting means and apply forces to said valve adjusting means in the direction of movement of said valve adjusting means.