Patent ID: 7918652

Claim:
A dovetail structure of a fan that attaches the fan to a portion around a discoid disc rotationally driven by a turbine, wherein the fan has an inlet hub diameter smaller than an outlet hub diameter, wherein the disc has a plurality of dovetail grooves extending, at a fixed first angle with respect to an axis of a rotation, from a leading edge to a trailing edge of the disc, and spaced at a fixed second angle in a peripheral direction, and wherein the fan has a dovetail portion extending at the same angle as the first angle of the dovetail grooves and the dovetail portion is fittable to the dovetail groove, in an inner end of the fan, wherein the dovetail portion of the fan comprises: (a) a main dovetail portion extending to a trailing edge of the fan from an intermediate portion and the main dovetail portion is fittable to the dovetail groove of the disc: and (b) a plurality of sub dovetail portions extending to the intermediate portion from a leading edge of the fan; wherein the dovetail structure further comprises a spin cone fixable to the disc, wherein the spin cone is disposed on a front side of the fan, and the spin cone has a plurality of sub dovetail grooves fitted to the plurality of sub dovetail portions in an inner peripheral portion of the spin cone, wherein a platform portion comprising an inner peripheral surface of an air flow path of the fan has a first taper side portion having a fixed slope in which a width or the first taper side portion, in a peripheral direction, is narrower on a rear side of the fan than on the front side of the fan, and wherein the disc has a taper projection portion fitted to the first taper side portion.