583,577. Louvre windows and ventilators. HILTON, P. K., and WEBB, N. Nov. 4, 1944, No. 21639. [Classes 20 (iii) and 137] In a louvre window or ventilator comprising pivoted panels 2 adapted to be opened and closed in unison by means of a coupling bar 7, the pivots 3 pass through holes in a frame member 4 of channel section having an outwardly presented open side, and carry arms 6, these arms and the coupling bar being concealed in the frame. In the form shown, the coupling bar is connected by a link 12 to an arm 11 on the spindle 9 operated by an external handle 8. The link is arched to make it springy and is so constructed that when the louvres are closed the arm 11 passes over a dead-centre position, thus locking the panels and preventing rattling.