Abstract: An improved pneumatic thermostat is provided which is capable of generating from a variable pressure air supply a pressurized air signal indicative of ambient temperature. The thermostat is used in conjunction with an air flow regulator in an air distribution system and utilizes as an air supply a portion of the air flow being distributed. The thermostat utilizes a pressure reducing valve which is referenced to pressure downstream from the air flow regulator, a flapper and nozzle pneumatic mechanism activated by a bi-metallic lever, and a self-aspirating arrangement which insures the bi-metallic lever is continuously sensing the true ambient temperature.

Abstract: A fluid flow regulating device for use in fluid handling systems which is capable of maintaining substantially constant flow rates over a wide range of variations in system pressure. The device includes a housing having disposed therein a conduit whose lateral wall includes one or more apertures of a predetermined configuration. A piston is disposed within the conduit and is axially displaceable, in response to pressure differentials, throughout the portion of the conduit wherein the apertures are located. A spring mechanism having a specified non-linear coefficient of stiffness is employed to yieldably resist downstream displacement of the piston. The piston and aperture together form a variable area flow passageway through which substantially all the fluid must pass. A pneumatic, thermometric mechanism may also be employed to displace the piston within the conduit in response to changes in temperature and independent of pressure variations.