BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to umbrellas and more particularly to an FRP (fiber glass reinforced plastics) umbrella frame with characteristics such as enhanced strength, quick assembly, and reduced size after folded. 
     2. Description of Related Art 
     Umbrella frame designs take many different forms. A conventional umbrella having a two-section rib is shown in FIG.  9 . Such umbrella frame has a number of disadvantages as observed by the present inventor. For example, a rivet is used in each of five pivot joints P 1  to P 5 . However, it is known that riveting is a tedious task. Also, uniform quality of riveting on the pivot joints P 1  to P 5  for each frame element is not easy to control. Typically, there are about total 30 to 40 pivot mechanisms in an umbrella frame. Unfortunately, one defective pivot mechanism will make the whole umbrella unusable after a short period of time due to rust in the pivot mechanisms. Further, stress tends to concentrate on the pivot mechanisms. As a result, the frame is susceptible of break in folding or expanding the umbrella. 
     An FRP umbrella for solving the problem of rust in the pivot mechanisms caused by riveting is proposed. However, the FRP umbrella still suffered from several disadvantages. For example, ribs of the FRP umbrella frame are shaped as cylinders for providing a sufficient support to the frame. Also, a variety of plastic molded connecting elements and pivot elements are fitted at two ends and in intermediate section of the cylindrical rib, respectively. As such, each frame element is increased in size, resulting in a bulky FRP frame. This can cause difficulties in storage, packing, and delivery of the umbrella. Hence, a commercialized FRP umbrella is still not available after such technique has been developed for more than 20 years. Thus, continuing improvements in the FRP umbrella frame are constantly being sought. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an FRP umbrella frame having advantages such as enhanced strength, quick assembly, and much reduced size after folded. 
     It is another object of the present invention to provide a lightweight FRP umbrella frame for facilitating storage, packing, and delivery. 
     It is a further object of the present invention to provide an enhanced FRP umbrella frame for prolonging a useful life. 
     The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of frame of a FRP umbrella according to a first preferred embodiment of the invention; 
     FIG. 2 is a perspective view of an frame element of FIG. 1; 
     FIG. 3 is an exploded perspective view of FIG. 2; 
     FIG. 4 is a side elevational view in part section of an outer rib connection portion of FIG. 1; 
     FIG. 5 is a side elevational view showing the frame being folded; 
     FIG. 6 is a side elevational view showing the frame in a folded position; 
     FIG. 7 is a perspective view of a rib connection portion of an FRP umbrella according to a second preferred embodiment of the invention; 
     FIG. 8 is an exploded perspective view of FIG. 7; and 
     FIG. 9 is a side elevational view of partial frame of a conventional umbrella having a two-section rib. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 to  4 , there is shown an FRP umbrella frame  50  according to a first preferred embodiment of the invention. Note that components such as a hub  52  on a top of a shank  51 , a plurality of ribs  520  radially extended outwardly from the hub  52 , upper and lower rings  53 ,  54  both slidably sleeved on the shank  51 , a spring (not numbered as part of automatic umbrella) biased between the upper and lower rings  53 ,  54 , a plurality of corresponding spreaders  530 ,  531  joined between the ribs  520  and the upper ring  53 , and a plurality of corresponding auxiliary stretchers (as part of automatic umbrella)  540  joined between the spreaders  530 ,  531  and the lower ring  54  will not be described in detail below because they are well known except the spreaders  530 ,  531  and portions connecting the ribs  520 ,  521  and the spreaders  530 ,  531  critical to the invention. 
     As shown, in an inner rib connection portion there is provided a second pivot mechanism  10  at about middle sections of the spreaders  530 ,  531 . The second pivot mechanism  10  includes an elongate connector  11  having two parallel first and second channels  110 ,  111 , an inverted U-shaped attachment member  12  having one end coupled to the connector  11 , and an extension sleeve  13  coupled to the other end of the attachment member  12 , the extension sleeve  13  including a third channel  130  is aligned with the first channel  110 . A slope  121  is extended from an underside tunnel  120  of the attachment member  12  to one end of the extension sleeve  13  for facilitating a cylindrical cross bar  43  of a second pivot connecting member  40  to move into the tunnel  120 . One spreader  530  passes through the first channel  110  and the third channel  130  while the other spreader  531  passes through the second channel  111 . 
     In an outer rib connection portion, there are provided the following elements. A first pivot connecting member  20  includes first and second bores  21 ,  22  for receiving outer ends of the spreaders  530 ,  531  respectively, a rectangular opening  23  at the other end opposite to the first and second bores  21 ,  22 , and a cylindrical cross bar  24  at an outer side of the opening  23 , the cross bar  24  being pivotably coupled to a first pivot mechanism  30 . A width of the first pivot mechanism  30  is slightly smaller than that of the opening  23  of the first pivot connecting member  20  so that one end of the first pivot mechanism  30  can pass the opening  23  in assembly. At one end of the first pivot mechanism  30  toward the first pivot connecting member  20  there are formed a connector  31  and a through hole  310  at an open end of the connector  31 . A fixing hole  311  is provided at one end of the first pivot mechanism  30  and the other end of the first pivot mechanism  30  also provided with a channel  312  for passing the lower rib  521  therethrough. A U-shaped tunnel  32  is formed on a central portion of the first pivot mechanism  30 . A slope  33  is formed at a side of the tunnel  32  coupled to the connector  31  for facilitating the cross bar  24  of the first pivot connecting member  20  to move into for engagement. 
     The second pivot connecting member  40  has a bore  41  at one end for receiving and fixing the outer end of the upper rib  520  and a rectangular opening  42  at the other end, the opening  42  having a width slightly larger than that of the attachment member  12  of the second pivot mechanism  10 . Hence, the opening  42  can pass the extension sleeve  13  and the slope  121  to position in the tunnel  120  of the attachment member  12 . The cylindrical cross bar  43  is formed at an outer side of the opening  42 . A recess  45  is formed beside the opening  42 , and a third opening  44 A is formed within the recess  45  extending through the second pivot connecting member  40 . A U-shaped hook member  44  is nested in a third opening  44 A. A rod  60  has one hook end  61  hooked with the hook member  44  and the other hook end  62  inserted through the hole  310  for fastening the second pivot connecting member  40  and the first pivot mechanism  30  together. 
     In assembly, insert the upper rib  520  into the bore  41  of the second pivot connecting member  40  for fastening. Next, pass the cross bar  43  through the slope  121  to anchor in the tunnel  120  of the attachment member  12  for pivotably coupling the opening  42  of the second pivot connecting member  40  to the attachment member  12  of the second pivot mechanism  10 . Then insert the spreader  530  through the first channel  110  and the third channel  130  into the first bore  21  and insert the spreader  531  through the second channel  111  into the second bore  22  respectively for parallel fastening. As such, the cross bar  43  of the second pivot connecting member  40  will be closed within the tunnel  120  and can pivot about the tunnel  120  of the second pivot mechanism  10 . Next, pass the opening  23  of the first pivot connecting member  20  through the connector  31  and the slope  33  to anchor in the tunnel  32  of the first pivot mechanism  30  and then insert the lower rib  521  from the channel  312  into the fixing hole  311  of the first pivot mechanism  30 . As such, the cross bar  24  will be closed within the tunnel  32  and permitting the cross bar  24  to pivot about the tunnel  32 . Finally, hook the hook end  61  of the rod  60  through the hook member  44  and the other hook end  62  thereof through the hole  310  for fastening the second pivot connecting member  40  and the first pivot mechanism  30  together. As an end, a complete frame is formed. 
     In order to reduce the size of folded umbrella frame, in addition to lower the width of the pivot connecting member and the pivot mechanism, there are provided a both side recesses  25 ,  45  at the main surface of the first and second pivot connecting members  20  and  40 , respectively (as shown in FIGS.  2  and  3 ). 
     Referring to FIGS. 5 and 6, a folding operation of the expanded frame  50  will now be described in detail below. First, slide down the upper and lower rings  53 ,  54  along the shaft  51  as indicated by arrow A 1 . At the same time, the spreaders  530 ,  531  move downward to cause the second pivot mechanism  10  to move inward and downward as indicated by arrow A 2 . The second pivot connecting member  40  then pivot about the second pivot mechanism  10  to form a larger angle therebetween. Next, the rods  60  moved by the second pivot connecting member  40  further cause the first pivot mechanism  30  to pivot. Also, the lower ribs  521  extended outward from the first pivot mechanism  30  fold toward the spreaders  530 ,  531  as indicated by arrow A 3 . Finally, a folded frame  50  with the spreaders  530 ,  531  and the ribs  520 ,  521  in close proximity to the shaft  51  is formed, as shown in FIG.  6 . In view of the above, the invention can effect a quick, smooth folding or expanding operation. 
     Referring to FIGS. 7 and 8, there is shown an FRP umbrella frame according to a second preferred embodiment of the invention. The first and second preferred embodiments are substantially the same except the following as detailed below. In the second preferred embodiment a single spreader is employed. The second pivot mechanism  10  has a single first channel  110  and the first pivot mechanism  30  has a single first bore  21  respectively. Accordingly, widths of the connectors  11 ,  31  are decreased for being adapted to the second pivot connecting member  40  and the first pivot connecting member  20  respectively. Hence, the second preferred embodiment is suited to smaller umbrella frame. 
     It is to understood that in order to further reduce the size of the umbrella frame of the present invention after being folded, in the embodiment of the invention there are provided a recess  25  and  45  on the first and second pivot connecting member, respectively and an inner free end of the connector  31  of the first pivot mechanism  30  having a curving portion to enable the first and second pivot connecting member and the first and second pivot mechanism to be folded as closer as possible after folded, as shown in FIGS. 2,  6  and  7 . 
     In brief, the spreaders and the upper and lower ribs are supported by a four-sided structure including of the first and second pivot connecting members, the first and second pivot mechanisms, and the rods being pivotably coupled together. 
     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.
A folded umbrella frame has a plurality of units each comprising a second pivot mechanism, a first pivot mechanism fixed to the lower rib, a first pivot connecting member pivotably coupling to the first pivot mechanism, a second pivot connecting member receiving the upper rib and pivotably coupling to the second pivot mechanism and a steel rod hooking the second pivot connecting member and the first pivot mechanism together. The spreader passes through the channels of the second pivot mechanism to receive in the first bore of the first pivot connecting member. The invention effects a smooth folding by employing no rivet and a reduced size after folded.