Patent ID: 8561520

Claim:
A brake servo for motor vehicles comprising: a servo housing, an interior space of which is divided by a movable wall into a vacuum chamber and a working chamber, a control housing which bears the movable wall and in which is arranged a control valve which controls a pneumatic pressure difference acting on the movable wall and which can be actuated both by an actuating rod via a valve piston and also, independently of the actuating rod, by an electromagnet, three sealing seats arranged concentrically with respect to one another and of a valve body which interacts with the sealing seats, wherein a first sealing seat is formed in the control housing and a second sealing seat is formed on the valve piston, and a third sealing seat is formed on a sleeve which interacts with the electromagnet, an annular element which is arranged so as to be movable relative to the third sealing seat and which is arranged radially within the sleeve, and wherein the valve piston has a further concentric sealing seat which projects axially beyond the second sealing seat, with the further sealing seat having at least one recess.