Pneumatic booster with solenoid auxiliary control, particularly for motor vehicle brake systems

A pneumatic booster with solenoid auxiliary control, particularly for motor vehicle brake systems, having

• a booster housing (10) in which at least a first chamber (12) and a second chamber (14) are contained and are separated from each other by a movable wall (16),
• a valve body (22) which is connected to said movable wall (16) for common axial relative movement with reference to said booster housing (10) and having
• a first valve seat (24),
• a sealing element (60) arranged axially movable in said valve body (22) and pretensioned in the direction of said first valve seat (24),
• a piston (42) which is movable by means of an actuator element (44) axially away from said sealing element (60),
• a valve barrel (30) having
• a second valve seat (32) assigned to said sealing element (60), pretensioned in the direction of said sealing element (60), couplingly connected to said piston (42) for movement in the direction away from said sealing element (60) and also movable in the direction away from sealing element (6) by means of a solenoid (40) independently of said piston (42),
• a seal (56) between said valve barrel (30) and said piston (42),
• a stopper element (52) defining a common rest position of said piston (42) and said valve barrel (30) in which said first chamber (12) is sealed off from the inflow of air and is connected to said second chamber (14), and
• a passage (26) through which air flows into said first chamber (12) when said valve barrel (30) leaves its rest position, said sealing element (60) being in contact with said first valve seat (24) and discontinuing the connection between said two chambers (12, 14), characterized in that said seal (56) is axially effective between said valve barrel (30) and said piston (42) and disposed so that it will only seal when an abutment (55) formed on said valve barrel (30) is in contact at least more or less with a coupling element (54) formed on said piston (42).