Double circuit controlled brake pressure control valve.
1. Dual-circuit-controllable brake pressure control valve for compressed air-operated vehicle brake systems, in particular a trailer control valve, having the following features : a) there is provided a first control piston (7, 14) which bounds a first control chamber (2) and is loaded by a control pressure from a first brake circuit ; b) there is provided a second control piston (11) which bounds a second control chamber (46) and is movable relative to the first control piston (7, 14) and is loaded by a control pressure from a second brake circuit, and is so arranged that the two control pistons (7, 14, 11) are each movable in the same direction in dependence on the respective associated control pressures ; c) there is provided a combined inlet and outlet valve (37, 38, 48) which serves for the selective connection of a pressure medium inlet chamber (25) to a working chamber (21) and also to a pressure medium outlet (22) connected to the working chamber (21) and leading to the trailer brake circuit, or to a venting port (31) ; d) the combined inlet and outlet valve (37, 38, 48) is arranged to be operated in each case in dependence on the control pressure of at least one of the two control pistons (7, 14; 11) ; e) the two control pistons (7, 14; 11) are arranged to telescope together and so that they can be displaced relative to one another ; f) between the wall of a housing aperture guiding the outermost, first control piston (7, 14) and an annular wall of the outermost first control piston (7, 14) there is arranged a first sealing element (13) which seals the first control chamber (2) bounded by the outermost first control piston (7, 14) ; g) the second control chamber (46) is sealed directly from a partial chamber (47), which can be connected to the working chamber (21) and thus to the trailer brake circuit, by means of a second sealing element (12) ; characterized by the following features : h) between the inner side of the annular wall (14), facing the second control piston (11), of the first control piston (7, 14) and the outer edge of the second control piston (11) facing this wall (14) there is arranged the second sealing element (12) which prevents escape of pressure medium from the second control chamber (46) ; i) both control chambers (2, 46) are sealed directly from the partial chamber (47) by respective associated sealing elements (12, 13).