Control valve

The control valve (1) has a pressure chamber (12) with a high pressure port (15) and a low pressure port (16). The mouth (17) of the LP port is located in the casing wall (13) which forms a stop for the shut-off head (4) of a control piston (2). The diameter (6) of the shut-off head is greater than the guide diameter (7) of the control piston, and the step diameter which corresponds to the offset from the shut-off diameter to the guide diameter lies in the pressure chamber.