Umbrella frame structure for two-fold inverted umbrella

An umbrella frame structure for a two-fold inverted umbrella, comprising:

• an umbrella shaft assembly comprising an umbrella shaft, a handle connected to one end of said umbrella shaft, an upper nest connected to an opposite end of said umbrella shaft and a lower nest sleeved onto said umbrella shaft and axially movable back and forth relative to said upper nest, said lower nest comprising a plurality of positioning grooves equiangularly spaced around the periphery thereof, a plurality of locating grooves equiangularly and transversely spaced around the periphery thereof and respectively disposed in communication between each two adjacent said positioning grooves and a pivot positioning member located in each said locating groove;
• and
• a plurality of rib assemblies, each said rib assembly comprising a main rib, a sub rib, a stretcher and a tip, said tip connecting one end of said main rib and one end of said sub rib, said stretcher having one end thereof connected to a part of said main rib between two opposite ends of said main rib and an opposite end thereof disposed in one respective said positioning groove, said main rib having an opposite end thereof pivotally connected to said upper nest of said umbrella shaft assembly, said sub rib having an opposite end thereof disposed in one respective said positioning groove, the end of said sub rib and the end of said stretcher that are disposed in one respective said positioning groove being pivotally connected together by the respective said pivot positioning member;
• wherein said sub rib comprises a connector and a sub rib body, said connector comprising a flat connection portion located at one end thereof and a positioning through hole located at an opposite end thereof, said sub rib body having one end thereof positioned in said positioning through hole of said connector and an opposite end thereof connected to the said main rib of one respective said rib assembly by one respective said tip;
• said stretcher comprises an elongated base wall and two opposite side walls respectively extended from two opposite lateral sides of said elongated base wall;
• and
• said flat connection portion of said connector is disposed between the said two opposite side walls of one respective said stretcher and pivotally connected to one end of one respective said stretcher in one respective said positioning groove by one respective said pivot positioning member.