Device and method for the supply and venting of compressed air in spring-applied/pressure-released brakes and parking brake

The valve assembly (10) to charge and bleed the spring store cylinders (12), for the brakes of heavy commercial motor vehicles, has two magnetic valves (14,16) and a 3/3 valve (18), with a housing (20) for at least three control pistons (22,24,26) and a switch piston (28). The switch piston can be moved into a variety of conditions, through the working surfaces of the control pistons, linked to control chambers (30,32) at selective pressure levels. The structure can be set into configurations for charging, bleeding, and an intermediate condition so that the setting of the switch piston can determine the state of at least one spring store cylinder. The switch piston has a number of thicker zones (38,40,42) with seals (44,46,48), so that sections of the piston are sealed against a housing wall (50) of the 3/3 valve.