894,981. Window &c. operating mechanisms; ventilators. SLIGHTING INSTITUUT VOOR TUINBOUWTECHNIEK. Sept. 17, 1958 [Sept. 17, 1957], No. 29778/58. Classes 20(3) and 137 [Also in Group XXIV] Two ventilating windows 21, 22 of a greenhouse movable between a preferential biased closed position under spring force or gravity and a terminal 'open position are operated alternately by a mechanism comprising sun gears 7, 8 on the respective shafts 9, 10 and chain driven through planetary gears 5, 6 of different numbers of teeth and secured to a pulley 3 driven from a motor 1, so that when, say window 21 is in its closed position and shaft 9 is held, then shaft 10 is rotated through reduced gear ratio to open window 22. On reversal of the motor 1, window 22 closes helped by its weight or spring force and when fully closed, the shaft 10 is held and shaft 9 is driven through a reduced gear ratio to open window 21. Locking devices 23, 24 lock the shafts in any desired position of the windows. Specification 632,380 is referred to.
