referring to fig1 and 3 , an umbrella frame 10 ( e . g ., one formed of frp ) in accordance with a preferred embodiment of the invention comprises a shank 11 including a plastic top hub 12 having a plurality of slots 120 equally spaced therearound , and a plastic lower sleeve 13 slidably put on the shank 11 and having a plurality of slots 130 equally spaced therearound . an plastic upper connecting rod 20 has a flat portion 200 at one end fitted in and pivotably connected to one slot 120 and a plastic lower connecting rod 21 has a flat portion 210 at one end fitted in and pivotably connected to one slot 130 . each of the connecting rods 20 and 21 is formed of plastic material . the other end of each of the connecting rods 20 and 21 is formed with a bore 201 or 211 for snugly receiving one end of a first rib segment 14 or a strut 15 . a plastic u - shaped first connecting member 30 comprises a u - shaped recess 302 in its intermediate portion , a tubelike first extension 300 extended from one end of the recess 302 and having a bore 3000 therethrough , and a tubelike second extension 301 extended from the other end of the recess 302 and having a bore 3010 therethrough . the bores 3000 and 3010 are in communication through the recess 302 . thus , the strut 15 is adapted to insert through the bore 3000 , the recess 302 , and the bore 3010 . a lower slope 303 is formed between bottom of the second extension 301 and the recess 302 . the umbrella frame 10 further comprises a plurality of frp radial ribs each consisting of four rib segments namely first rib segment 14 , second rib segment 16 , third rib segment 17 , and fourth rib segment 18 . the first pivotal member 40 made of plastic is a substantially y - shaped element and comprises a bore 400 at one end for snugly receiving the other end of the first rib segment 14 , a cylindrical seat 401 across both ends of two branch of its bifurcation 408 with the recess 302 fitted thereon , an indentation 407 also across the branches of the bifurcation 408 , a first opening 402 defined by the bifurcation 408 , the indentation 407 , and the seat 401 , a second opening 403 defined by the bifurcation 408 and the indentation 407 , an enlarged cavity 404 formed at bottom of the second opening 403 , a u - shaped element 405 with its both ends 4050 fitted in the cavity 404 and with its intermediate portion projecting from the second opening 403 , and an arc member 406 at either side of the bifurcation 408 . thread leaving canopy can insert in and out of the arc member 406 for fastening canopy onto the ribs . a second pivotal member 41 made of plastic is a substantially y - shaped element and comprises a bore 410 at one end for snugly receiving the other end of the strut 15 , a cylindrical seat 411 across both ends of two branch of its bifurcation 418 , an indentation 417 also across the branches of the bifurcation 481 , a first opening 412 defined by the bifurcation 418 , the indentation 417 , and the seat 411 , a second opening 413 defined by the bifurcation 418 and the indentation 417 , an enlarged cavity 414 formed at bottom of the second opening 413 , a u - shaped element 415 with its both ends 4150 fitted in the cavity 414 and with its intermediate portion projecting from the second opening 413 , and an arc member 416 at either side of the bifurcation 418 . thread leaving canopy can insert in and out of the arc member 416 for fastening canopy onto the ribs . a plastic u - shaped second connecting member 31 comprises a u - shaped recess 312 in its intermediate portion with the seat 411 fitted therein , a tubelike first extension 310 extended from one end of the recess 312 and having a bore 3100 therethrough , an arc flat element 3101 extended from the first extension 310 , the flat element 3101 having a hole 3102 through its free end , a tubelike second extension 311 extended from the other end of the recess 312 and having a bore 3110 therethrough , the bore 3110 being in communication with the bore 3100 through the recess 312 such that one end of the second rib segment 16 is adapted to insert through the bore 3100 , the recess 312 , and the bore 3110 , and an upper slope 313 formed between top of the second extension 311 and the recess 312 . a third pivotal member 42 made of plastic is identical to the substantially y - shaped first pivotal member 40 and comprises a bore 420 at one end for snugly receiving the other end of the second rib segment 16 , a cylindrical seat 421 across both ends of two branch of its bifurcation 428 , an indentation 427 also across the branches of the bifurcation 428 , a first opening 422 defined by the bifurcation 428 , the indentation 427 , and the seat 421 , a second opening 423 defined by the bifurcation 428 and the indentation 427 , an enlarged cavity 424 formed at bottom of the second opening 423 , a u - shaped element 425 with its both ends 4250 fitted in the cavity 424 and with its intermediate portion projecting from the second opening 423 , and an arc member 426 at either side of the bifurcation 428 . thread leaving canopy can insert in and out of the arc member 426 for fastening canopy onto the ribs . a plastic u - shaped third connecting member 32 is identical to the plastic u - shaped second connecting member 31 and comprises a u - shaped recess 322 in its intermediate portion with the seat 421 fitted therein , a tubelike first extension 320 extended from one end of the recess 322 and having a bore 3200 therethrough , an arc flat element 3201 extended from the first extension 320 , the flat element 3201 having a hole 3202 through its free end , a tubelike second extension 321 extended from the other end of the recess 322 and having a bore 3210 therethrough , the bore 3210 being in communication with the bore 3200 through the recess 322 such that one end of the third rib segment 17 is adapted to insert through the bore 3210 , the recess 322 , and the bore 3200 , and a lower slope 323 formed between bottom of the second extension 321 and the recess 322 . a fourth pivotal member 43 made of plastic is identical to the substantially y - shaped first pivotal member 40 and comprises a bore 430 at one end for snugly receiving the other end of the third rib segment 17 , a cylindrical seat 431 across both ends of two branch of its bifurcation 438 , a lower indentation 437 also across the branches of the bifurcation 438 , a first opening 432 defined by the bifurcation 438 , the indentation 437 , and the seat 431 , and an arc member 436 at either side of the bifurcation 438 . thread leaving canopy can insert in and out of the arc member 436 for fastening canopy onto the ribs . a plastic u - shaped fourth connecting member 33 is identical to the plastic u - shaped second connecting member 31 and comprises a u - shaped recess 332 in its intermediate portion with the seat 431 fitted therein , a tubelike first extension 330 extended from one end of the recess 332 and having a bore 3300 therethrough , an arc flat element 3301 extended from the first extension 330 , the flat element 3301 having a hole 3302 through its free end , a tubelike second extension 331 extended from the other end of the recess 332 and having a bore 3310 therethrough , the bore 3310 being in communication with the bore 3300 through the recess 332 such that one end of the fourth rib segment 18 is adapted to insert through the bore 3310 , the recess 332 , and the bore 3300 , and a lower slope 333 formed between bottom of the second extension 331 and the recess 332 . the other end ( i . e ., free end ) of the fourth rib segment 18 is secured to canopy in a manner known in the art . in assembly , a first link 50 includes a first hook 51 at one end passed the projecting intermediate portion of the u - shaped element 405 and fastened thereat , and a second hook 52 at the other end passed the hole 3102 and fastened thereat . a second link 60 includes a first hook 61 at one end passed the projecting intermediate portion of the u - shaped element 415 and fastened thereat , a second hook 62 at the other end passed the hole 3202 and fastened thereat , and a u - shaped intermediate member 63 engaged an outer surface of the second rib segment 16 . a first sleeve 160 loosely put on the u - shaped intermediate member 63 and the second rib segment 16 such that the first sleeve 160 is adapted to slide on the second rib segment 16 in a folding or extending operation of the umbrella . similarly , a third link 70 includes a first hook 71 at one end passed the projecting intermediate portion of the u - shaped element 425 and fastened thereat , a second hook 72 at the other end passed the hole 3302 and fastened thereat , and a u - shaped intermediate member 73 engaged an outer surface of the third rib segment 17 . a second sleeve 170 loosely put on the u - shaped intermediate member 73 and the third rib segment 17 such that the second sleeve 170 is adapted to slide on the third rib segment 17 in a folding or extending operation of the umbrella . for extending the umbrella , simply push the lower sleeve 13 upward from the position of fig5 to the position of fig4 via the position of fig3 . to the contrary , for folding the umbrella , simply push the lower sleeve 13 downward from the position of fig4 to the position of fig5 via the position of fig3 . either extending or folding operation is made smooth due to the advantageous characteristics discussed above . moreover , the arc flat element extended from one end of the second connecting member 31 , the second connecting member 32 , or the third connecting member 33 is adapted to decrease size of the folded umbrella . further , the indentations 407 , 417 , 427 , and 437 of the first , second , third , and fourth pivotal members 40 , 41 , 42 , and 43 are adapted to facilitate extending or folding operation of the umbrella and cause rib segments to dispose in a more parallel configuration after folding , thereby further decreasing size of the folded umbrella ( see fig5 ). while the invention herein disclosed has been described by means of specific embodiments , numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims .
provided is a fiberglass reinforced plastic umbrella frame comprising ribs each consisting of four segments wherein first rib segment and one strut are connected together by one of u - shaped connecting members and one of y - shaped pivotal members having a cylindrical seat across both ends of its bifurcation , and any two adjacent rib segments are connected together by the u - shaped connecting member and the y - shaped pivotal member . there are also provided links each for connecting the pivotal member and the distal connecting member . the umbrella can carry out a smooth folding or extending operation and has a reduced folded size and enhanced structural strength .