Patent ID: 8671823

Claim:
A pneumatic brake servo comprising: a servo housing divided into at least one working chamber and at least one vacuum chamber by at least one axially movable wall, wherein the axially movable wall is actuable by a pneumatic differential pressure; an actuable input member including a valve piston; a control valve arranged in a control housing, wherein the control valve is actuable by the valve piston for controlling the pneumatic differential pressure; an elastic reaction element arranged in a recess of the control housing; an output member positioned to bear on the elastic reaction element and act on a master brake cylinder with an output force, wherein the actuable input member acts on the elastic reaction element with an input effective area (A 1 ) and the output member acts on the elastic reaction element with an output effective area (A 2 ) and the ratio of output effective area (A 2 ) to input effective area (A 1 ) determines a force boost ratio of the brake servo; and means for manually adjusting the output effective area (A 2 ), wherein the means for manually adjusting the output effective area is an adjusting element including a disk-shaped section, with the disk-shaped section of the adjusting element being arranged so as to be guided in a recess of the output member that faces the reaction element and having a diameter (D 1 ).