DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring to FIGS. 1 to 5, the invention comprises an inner rib 11, a middle rib 12, an outer rib 13, and a secondary rib 2. Wherein, the middle rib 2 is formed by pivotally connecting a front strut 121 and a rear strut 122.

[0020] The inner rib 11 has one end thereof pivotally connected to an upper nest 3, and the other end thereof pivotally connected to a middle section of the secondary rib 2.

[0021] The upper nest 3 is fastened at one end of a post 4, whereas the other end of the post 4 is penetrated through inner openings of a middle nest 5 and a lower nest 6, and the middle nest 5 and the lower nest 6 is supported by a compression spring 51 in between. The secondary rib 2 has one end thereof pivotally connected to the middle nest 5, and the other end thereof pivotally connected to the front strut 121. An outer end of the rear strut 122 is pivotally connected to the outer rib 13. The secondary rib 2 is a solid shaft. Pivotal connection portions of the secondary rib 2 with the inner rib 11 and the secondary rib 2 with the connection rib 8 are disposed with a middle junction 8, respectively. Also, each of the pivotal connection portions of the secondary rib 2 is provided with a pre-formed bent portion 21. The middle junction 8 is clamped and fastened around the secondary rib 2; that is, the middle junction 8 is a U-shaped body wrapping around an outer periphery of the secondary rib 2.

[0022] When stretching the umbrella, the middle nest 5 is impelled upward using actions of the compression spring 51 between the middle nest 5 and the lower nest 6. The secondary rib 5 is driven and stretched by the middle nest 5, and the inner rib 11, front and rear struts 121 and 122, the outer rib 13, and the connection rib 7 are also stretched in sequence. In the meanwhile, the connection rib 7 also pulls the lower nest 7 to move upward, and the umbrella becomes completed stretched. Wherein, the secondary rib 2 is a solid shaft, pivotal connection portions of the secondary rib 2 with the inner rib 11, and the secondary rib 2 with the connection rib 8 are disposed with a middle junction 8, respectively, and corresponding openings are disposed at the middle junctions 8. Therefore, without requiring provision of connection openings at the secondary rib 2, flexibility strength of the secondary rib 2 is ensured for lowering chances of bending. Furthermore, a volume of the secondary rib 2 is effective reduced, thereby substantially decreasing an entire volume of the collapsed umbrella for easy portability.

[0023] Referring to FIG. 3, the bent portions 21 are pre-formed at locations where the middle junctions 8 wrap around the secondary rib 2. Wherein, the bent portion 21 pivotally connecting the inner rib 11 is bent toward the inner rib 11, and a pivotal axis 14 is penetrated into an axis opening 81 of the middle junction 8 and is exactly connected and fastened at an inner side of the bent portion 21. An end of the connection rib 7 for coordinating with the middle junction 8 is clasped in an interior of the middle junction 8 via a channel 82 of the middle junction 8, and is also precisely fastened at an inner indenture of the bent portion 21.

[0024] Referring to FIG. 6 showing a schematic view illustrating the connection between the secondary rib 2 and the middle junction 8 in another embodiment in accordance with the invention, wherein the bent portion 21 pivotally connecting the secondary rib 2 and the inner rib 22 is bent toward a reverse direction of the inner rib 11. The middle junction 8 is provided with an orifice 83 for coordinating with the bent portion 21 of the secondary rib 2, and the pivotal axis 14 is penetrated into the pivotal opening 81 of the middle junction 8.

[0025] Referring to FIG. 7 showing a schematic view illustrating the connection between the secondary rib 2 and the middle junction 8 in yet another embodiment in accordance with the invention, wherein the middle junction 8 is directly wrapped around the vertical secondary rib 2, and the middle junction 8 is provided with a connection portion for coordinating and connecting to the inner rib 11 and the connection rib 7.

[0026] Referring to FIG. 8 showing a structural view illustrating the inner rib 11 being formed with the middle junction 8 of the connection rib 7 as an integral, wherein the bent portion 21 at the secondary rib 2 for coordinating with the inner rib 11 and the connection 7 is bent toward a same direction as the secondary rib 2, and is also an integral with the secondary rib 2. The middle junction 8 is at the same time wrapped around the bent portion 21, and is disposed with the pivotal opening 81, and the channel 82 for connecting the connection rib 7.

[0027] It is observed from the above that, the rib assembly according to the invention provides practical values such as having higher flexibility strength for reducing chances of bending thereof, and minimizing a volume of an umbrella for easy portability. It is of course to be understood that the embodiment described herein is merely illustrative of the principles of the invention and that a wide variety of modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.