523,500. Ventilating greenhouses and other enclosures. TUCKER, H. Jan. 9, 1939, No. 727. [Class 137] In apparatus for the control of temperature in greenhouses or other enclosures by ventilation, a hinged panel 1 is connected by a system of links and levers 2 to 11 to a collar 12 adjustably mounted on a rod 13. This rod forms part of an automatic control device 15 comprising an electric motor 17 which causes the rod 13 to move in a guide 14, and a thermostatic element 18 controlling the motor. The adjustable thermostatic relay effects the rotation of the motor shaft in one or the other direction in the event of the temperature of the enclosure rising above or falling below the predetermined temperature for which the relay device has been set.
