Abstract: A fire damper or the like having butterfly-type gas flow control blades includes a heat responsive blade release assembly that incorporates a standard fusible link accessible from externally of the assembly. The fusible link holds together pivoted side plates of a housing from which extends a pair of arms normally holding the blades in their open positions. When the link melts, the side plates move apart, allowing the arms to open and release the blades. The assembly is also adjustable to vary the extent to which the blades open.

Abstract: A fire damper having a temperature-sensitive link assembly designed to permit ease of maintenance of the damper. In one embodiment, the link assembly includes a fusible link that extends across and holds the blades folded. At each end, the link is coupled to a bracket embracing the blades by a pivot pin and an associated latch that is manually releaseable. During maintenance of the damper, either latch can be released and the link will then swing down about the pivot pin at the opposite end of the link, permitting the damper blades to close. In normal use, the blades will also close in response to an over-temperature condition causing the fusible link to break. In an alternative embodiment, a plain non-fusible link is used and one of the latches is released by a temperature-sensitive actuator made of memory metal.

Abstract: A sensor has two independent pressure chambers, each of which is in fluid communication through a plurality of relatively small passages to the flow within a duct; the passages for the first chamber being directed upstream, the passages for the second chamber being directed otherwise than upstream, usually downstream. The chambers are arranged so that their axes are parallel to each other, with the axis of the first chamber upstream of the axis of the second chamber. Depending upon the profile of the sensor, the dynamic pressure and changes therein are a constant multiplier function of the first chamber pressure minus static pressure. The constant multiplier is greater than 1.0, and is constant for a given sensor across a wide variation of measured pressures. When the profile of the sensor is essentially cruciform, with upwardly and downwardly extending wings, the multiplier effect may be in the order of 3.5 to 5.0, thereby permitting very low differential pressures to be detected and measured.

Abstract: An air control damper is provided with an actuator coupled to a shaft for operating the blades of the damper. The actuator includes an electric drive motor that turns the shaft by way of a lever that is coupled to the shaft. The lever has a pulley at an outer end and a cable extends from the drive motor around the pulley and back to a fixed point adjacent the motor. When the motor is operated, the cable is wound around the motor drive shaft, pulling the lever towards the motor and turning the shaft. The arrangement provides a mechanical advantage in transmitting the motor output force to the blade actuating shaft.