Fan assembly with blades secured between two hub members

Claim 1

A fan comprising two hub members; a flat plate member sandwiched between said hub members; at least two blades, each blade having a short stem at the root thereof with a boss on the end of the stem remote from the blade which boss is secured between said two hub members, each hub member being semi-circularly notched to fit around said stem and each boss being of circular cross-section transverse to the axis of the boss, said axis being a radial axis of the fan, each boss further including a diametral groove formed in the boss at the root end of each blade for partially straddling the periphery of said plate member, each boss being smoothly curved in its longitudinal section with its maximum diameter intermediate its ends, the side surface of the boss merging smoothly into the end surface nearer the blade, which end surface is a portion of a spherical surface whose radius of curvature is equal to the distance of that surface from the center point of said flat plate member; and means securing said two hub members and plate together with said hub members at least partially embracing said bosses and with their outer peripheries adjacent one another in a diametral plane in the regions between said blades whereby said blades are held onto said plate; said hub members being of the same uniform shape in all radial planes to conform to and fit around the side and top of each boss, the peripheral portions of said hub members being smoothly curved in a plane transverse to said radial planes and containing said center point so as closely to embrace the spherical end surface of the boss on each of said blades; and the radially outermost portions of said hub members extending inwardly towards one another over part of the end surfaces of the boss adjacent the root of the fan blade.