US Patent 7690154 Channel-mounted 4-bar linkage assembly

A 4-bar linkage assembly for mounting a sash to a frame member of a window assembly. The linkage assembly including a vent bar having an offset portion and a base portion that fits within a sash channel of the sash. The vent bar includes a fixed connection extending between the offset portion and the base portion for supporting the offset portion and projecting between overhanging rails of the sash channel. The offset portion forms a stop which engages an end of the sash channel for locating the vent bar within the sash channel.