Abstract: An axial flow fan has a hub with a plurality of hub struts extending radially from the hub for mounting a blade on the end of each hub strut. Inner and outer studs extend in the axial direction of the fan on each of the hub struts. An air seal covers the hub struts, and particularly the space between the hub struts. The air seal has a generally round central sheet and a number of radially adjustable segments extending radially from the central sheet corresponding to the number of hub struts. Each of the segments is a generally trapezoidal sheet spanning the space between adjacent hub struts. Inner and outer slots along each of the radial edges of the trapezoidal sheet extend in a direction parallel to a radial line through the center of the sheet with each slot engaging a stud on a hub strut. This permits the segments to be adjusted radially to closely match the roots of the blades before nuts are tightened on the threaded studs.

Abstract: An axial flow fan has a hub with a plurality of hub struts extending radially from the hub for mounting a blade on the end of each hub strut. Inner and outer studs extend in the axial direction of the fan on each of the hub struts. An air seal covers the hub struts, and particularly the space between the hub struts. The air seal has a generally round central sheet and a number of radially adjustable segments extending radially from the central sheet corresponding to the number of hub struts. Each of the segments is a generally trapezoidal sheet spanning the space between adjacent hub struts. Inner and outer slots along each of the radial edges of the trapezoidal sheet extend in a direction parallel to a radial line through the center of the sheet with each slot engaging a stud on a hub strut. This permits the segments to be adjusted radially to closely match the roots of the blades before nuts are tightened on the threaded studs.

Abstract: A fan blade mounting system for large air-moving fans includes a radially extending hub strut, a blade root member pivotally coupled to an end of the hub strut for receiving a blade skin, and a tube end located between the blade root member and the hub strut. A pair of resilient mounts are utilized in the blade root member to effectively pivotally couple the blades to the hub, thus relieving most of the vertical bending moment transferred to the hub and eliminating critical frequencies associated with the fan. The hub strut is connected to the hub of the fan by a stud having right- and left-handed threads and a wall thickness adjacent to the threads sufficient for distributing the stresses substantially uniformly on the threads, thereby improving fatigue resistance. The resilient mounts comprise a metal core and metal sleeve with a resilient elastomeric layer between the core and sleeve. The sleeves are connected to the blade root member and the cores of the two mounts are clamped to the tube end.

Abstract: A large air moving fan has a number of hollow airfoil blades extending generally radially from a rotatable hub. The tips of the blades are surrounded by a circumferential shroud leaving a narrow gap between the tips of the blades and the shroud. A fin on the tip of each blade extends substantially perpendicular to the transverse cross section of the blade. The outline of the fin corresponds approximately to the shape the airfoil at the tip of the blade and the fin is curved so as to be substantially parallel to the shroud. It is believed that the fin prevents direct radial flow of a boundary layer of air from the outside surface of the blade into the gap between the tip of the blade and the shroud. This reduces the turbulence adjacent to the tip of the blade since the air traveling radially along the blade does not mix as violently with air passing through the gap from the high pressure side of the fan to the low pressure side of the fan. Noise reduction in the order of 3 db is obtained.