Power piston of booster

A power piston assembly for use in a booster, said assembly comprising:

• resilient diaphragm means within said booster for dividing the interior of said booster into two chambers, said diaphragm means having a first opening therethrough;
• rotatable piston plate means adjacent said diaphragm means for receiving the differential pressure caused by the pressure difference between said two chambers, said piston plate means having a second opening therethrough of non-circular configuration coaxially aligned with said first opening;
• and
• valve means adjacent the side of said diaphragm means opposite the side adjacent said piston plate means, extending through said first and second openings, and fitted against the side of said piston plate means opposite the side thereof and adjacent said diaphragm means for controlling communication between said two chambers and for resiliently holding said diaphragm means against said piston plate means, said valve means having:
• a main body portion adjacent said diaphragm means,
• a neck portion projecting axially from one end of said main body portion and extending through said first and second openings, and
• a head portion of non-circular configuration attached to the free end of said neck portion extending through said first and second openings, said head portion slidable through said first and second holes, and in contact with said rotatable piston plate means when said piston plate means is rotated relative to the position of said head portion.