Abstract: A non-biased security lock for a double-hung window assembly is disclosed as well as a method of securing a double-hung window assembly using the sash lock. One or more security locks are installed in one or more recesses in the stile of an outer window sash. In an open, or locked, position, a locking tab is rotatably disposed about a pivot pin substantially perpendicular to the stile of the outer window sash. The locking tab arrests further displacement of the inner window sash when the header of the inner window sash encounters the extended locking tab. The locking tab is restrained by a pair of pinions; hence any force or load applied to the locking tab is transferred as moment to the pinions. In a closed, or unlocked, position, the locking tab is rotatably disposed about the pivot pin so that the upper surface of the locking tab is flush with or substantially below the outer surface of the stile of the outer window sash so that the sash lock does not hinder relative movement of the window sashes.

Abstract: A non-biased security lock for a double-hung window assembly is disclosed as well as a method of securing a double-hung window assembly using the sash lock. One or more security locks are installed in one or more recesses in the stile of an outer window sash. In an open, or locked, position, a locking tab is rotatably disposed about a pivot pin substantially perpendicular to the stile of the outer window sash. The locking tab arrests further displacement of the inner window sash when the header of the inner window sash encounters the extended locking tab. The locking tab is restrained by a pair of pinions; hence any force or load applied to the locking tab is transferred as moment to the pinions. In a closed, or unlocked, position, the locking tab is rotatably disposed about the pivot pin so that the upper surface of the locking tab is flush with or substantially below the outer surface of the stile of the outer window sash so that the sash lock does not hinder relative movement of the window sashes.