Upon axial shift of the rotor, pin 1, actuated by spring 2, moves together with the shaft and, by means of nut 3, turns latch 4 about axis C. When the rotor shifts to the right a definite distance, latch 4 disengages valve member 6, which is raised by spring 5. At this, port a of the valve is closed and port b is opened, connecting the cylinder of the valve servomotor to the drain. As a result, the valve is closed and ceases to admit steam into the turbine.
$3980$LHP,FD$