When pedal 1, turning about fixed axis A (see Fig. a), is released, valve member 2 is pressed by spring 3 against lever 4, which turns about fixed axis B. At this, passage a, through which fluid is delivered, is connected to port d. Port d is connected to the working end of the power cylinder. When pedal 1 is depressed (see Fig. b), lever 4 depresses valve member 2, compressing spring 3. This blocks off passage a and port d is connected to chamber b which leads to the drain pipe. At the same time, plate valve member 5 is opened.
$3955$LHP,Va$