Patent ID: 7032496

Claim:
A vacuum servo brake for a booster brake system for motor vehicles, having an input member, by means of which a valve arrangement may be acted upon at an input force (F) in order to connect a working chamber selectively to the outside or to a vacuum chamber which is separated from the working chamber by a working piston which may be brought into operative connection with a main cylinder via an output member in order to generate a braking pressure (p) and on which there is provided an elastomeric reaction member through which a reaction force dependent on the braking pressure may be applied to the input member, in which the output member has a stop which, in the event of a predetermined input force (F), comes into abutment against the working piston to alter an amplification ratio of the vacuum servo brake; wherein, arranged adjacent to the elastomeric reaction member is at least one volume take-up means into which part of the elastomeric reaction member can flow in the event of the vacuum servo brake being actuated, said volume take-up means enabling an axial relative movement between the stop and the working piston so that the stop can come into abutment against the working piston in order to increase the amplification ratio of the vacuum servo brake, and wherein at least one of the stop and the working piston is of resilient construction in a region in which the stop abuts so that, when the stop abuts against the working piston, an axial relative movement between the output member and the working piston is still possible while further part of the elastomeric reaction member flows into the volume take-up means.