Fan central barrel coupling structure

A fan central tube coupling structure comprising a base having a bottom portion with a first section and a second section formed thereon;

• the first section standing relative to the bottom portion to upward extend and externally inwardly taper in an axial direction of the base;
• the second section being connected at a radially outer edge to the first section and having a radially inner free end that radially inward and horizontally extends to define a through hole on the base;
• the first section and the second section together defining an inward receiving recess tapering inwardly below the second section, and the inward tapered receiving recess being communicable with the through hole, wherein the first section is an annular wall of the inward receiving recess and the second section is a top wall of the inward receiving recess and one side of the first section facing the inward tapered receiving recess being an inward inclined wall and one side of the second section facing the inward tapered receiving recess being a downward-facing contact surface, on which an annular pressing groove is formed and a central tube having a top end and a bottom end and internally defining a receiving space;
• the top end defining an opening communicable with the receiving space;
• the bottom end being formed on around an outer surface with a first protruded section and a second protruded section located lower than the first protruded section, such that an engagement groove is defined between the first protruded section and the second protruded section;
• the second protruded section having an upward-facing contact surface and an interference pressing surface defined on an outermost peripheral surface of the second protruded section;
• and wherein the top end of the central tube is inserted through the through hole of the base from a lower side thereof, such that the second protruded section is press-fitted into the inward tapered receiving recess in the axial direction of the base, the interference pressing surface is radially outward forced against the inward inclined wall of the inward tapered receiving recess, and the free end of the second section of the base is fitted in the engagement groove and clamped in place by between the first protruded section and the second protruded section.