Tandem brake booster for automobiles

A motor vehicle tandem brake power booster, comprising:

• two booster units each comprising a switching device, a partition divided housing with a vacuum chamber and a working chamber, mechanical intermediate members, a piston separating the vacuum chamber from the working chamber wherein a pressure difference between a pressure in the vacuum chamber and a pressure that can be influenced by the switching device in a corresponding said working chamber in each booster unit acts on the piston separating the vacuum chamber from the working chamber and forces, which are proportional to the pressure difference and act on respective said pistons are bundled via the mechanical intermediate members by at least one transmission element each with forces applied by a driver of the vehicle to a corresponding brake pedal, the switching device of a first said booster unit having a first on-off valve actuated directly by the brake pedal for admitting pressure to the working chamber of said first booster unit and said switching device of a second of said booster units including a second unit on-off valve controllable as a function of pedal forces applied to the brake pedal and a speed with which the pedal is actuated for admitting pressure into the working chamber of the second booster unit, said working chamber of said second booster unit being isolated from said working chamber of said first booster unit.