Abstract: A fan damper includes a frame and a plurality of hollow airfoil blades, each having a leading edge, a trailing edge, a seal on the trailing edge, and a pivot mechanism on either end of each blade, including an extension having a weight. A secondary seal is positioned between the pivot mechanisms and the sides of the frame. A ladder bar connects the pivot mechanisms. During significant air pressure changes, the blades move against the weights from a first, closed, overlapping position, whereupon the seal on the trailing edge of a relatively upper blade seals against the leading edge of an adjacent relatively lower blade, and the secondary side frame seal seals against the pivot mechanisms, to a second, open position. When the air pressure decreases sufficiently, the blades return to the closed, overlapping position.

Abstract: A tubeaxial fan housing has a planar support vane that is fixed at sides thereof to opposing interior sides of the tubular housing, toward an inlet of the housing. The support vane receives a shaft on an underside thereof, upon which a propeller is mounted near an outlet end of the housing. The support vane has a curved edge facing the propeller to change a pattern of eddies generated downstream of the support plate and thereby reduce the noise generated by the fan. The curve is an S-shape and may be a sine wave whose period is ? the propeller diameter. The propeller is positioned a relatively large distance from the curved edge of the support vane to reduce further the generation of eddies. That is, the closest point of the curved edge to the propeller is one chord length, which chord is at a tip of a propeller blade. A rounded inlet bell on the housing includes a rounded surface to reduce further turbulence across the propeller and support vane to further reduce sound.

Abstract: A tubeaxial fan housing has a planar support vane that is fixed at sides thereof to opposing interior sides of the tubular housing, toward an inlet of the housing. The support vane receives a shaft on an underside thereof, upon which a propeller is mounted near an outlet end of the housing. The support vane has a curved edge facing the propeller to change a pattern of eddies generated downstream of the support plate and thereby reduce the noise generated by the fan. The curve is an S-shape and may be a sine wave whose period is ? the propeller diameter. The propeller is positioned a relatively large distance from the curved edge of the support vane to reduce further the generation of eddies. That is, the closest point of the curved edge to the propeller is one chord length, which chord is at a tip of a propeller blade. A rounded inlet bell on the housing includes a rounded surface to reduce further turbulence across the propeller and support vane to further reduce sound.

Abstract: A fan damper includes a frame and a plurality of hollow airfoil blades, each having a leading edge, a trailing edge, a seal formed on the trailing edge, and a pivot mechanism on either end of each blade, each of which pivot mechanisms includes an extension that includes a weight. A secondary seal is positioned between the pivot mechanisms and the sides of the frame. A ladder bar connects the pivot mechanisms. During significant air pressure changes, such as when a fan is turned on, the airfoil blades are caused to move, against the weights from a first, closed, overlapping position relative to the frame, whereupon the seal on the trailing edge of a relatively upper blade seals against the leading edge of an adjacent relatively lower blade, and the secondary side frame seal seals against the pivot mechanisms, to a second, open position. The airfoil blades will stay in the open position as long as the air pressure is enough to overcome the effect of the weights.

Abstract: A high specific speed fan propeller is provided which has a hub, at least two main blades and at least two auxiliary blades. The hub has an attachment device for connecting the propeller to a turning part. The at least two main blades are attached to the hub and extend radially a first distance therefrom. The at least two auxiliary blades are also attached to the hub and extend radially a second distance therefrom. The first distance is greater than the second distance.

Abstract: A method and apparatus for destratifying heat within an enclosure wherein a fan is positioned near the ceiling to draw warm air off the ceiling propelling same along a distribution tube also located near the ceiling and wherein the tube is provided with a plurality of openings along the bottom thereof through which the warm air is discharged toward the floor of the enclosure in the form of high velocity jets which entrain large quantities of surrounding ceiling air moving same to the vicinity of the floor of the enclosure.