Abstract:
A folding umbrella and particularly one having multiple folds, includes a support frame incorporating a hybrid rib typically located intermediate a main rib and a rear or outermost rib. The hybrid rib is formed of multiple sections composed of first and second materials which respectively provide the desired structural strength to reduce inversions of the umbrella to an acceptable minimum and provide the hybrid rib with the desired resiliency and flexibility to return the hybrid rib to its original, unstressed shape and thereby prevent permanent damage to the hybrid rib as well as adjoining frame elements of the umbrella. The thicknesses of the multiple sections and the relative sizes of the sections also significantly contribute to the capability of the hybrid rib to achieve the desired objectives of a compact, small, folding umbrella of reduced weight, and the ability to prevent permanent damage to the frame due to inversion.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/282,782, filed on Mar. 31, 2010, and the utility application Ser. No. 12/962,155 which is incorporated by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a compact, light-weight folding umbrella able to withstand bending without breaking and more particularly to a folding umbrella provided with ribs having a hybrid structure which significantly increase the structural strength of the umbrella without increasing the weight and size of the folding umbrella. 
     BACKGROUND 
     Compact, folding rain umbrellas and, more particularly, multiple fold umbrellas have a more complex frame structure, composed of many ligaments or ribs, as compared with foldable umbrellas having only a single fold. Folding umbrellas are particularly susceptible to breakage, especially those of the multiple fold design. Even a moderate wind force acting on the protective fabric of the umbrella will force the umbrella to invert since the force, although moderate, acts on a large surface area, much like the sail of a boat. This force is transferred to the frame structure supporting the protective fabric, causing the ribs to bend as they absorb this force. Ribs formed entirely of a non-elastic alloy, such as aluminum or steel, which experience such bending, remain distorted due to their lack of resilience and do not return to their original unbent shape, and thereby distort the entire support frame and degrade the normally smooth opening and closing operations of the umbrella. On the other hand, forming ribs of a material which is too flexible yields an umbrella which will invert too easily making it cumbersome and annoying to the user. The above problems affect all folding umbrellas and are more severe in the case of the multiple fold category. 
     Therefore, a design is needed to provide ribs having a proper balance of rigidity and flexibility sufficient to reduce inversion to an acceptable minimum, while providing sufficient elasticity to return the ribs back to their original shape in the event of an inversion. 
     OBJECTS OF THE INVENTION 
     One object of the present invention is to provide ribs for a compact, folding umbrella and especially a multiple-fold umbrella, which have a hybrid structure comprised of two different materials that cooperate to provide ribs having the strength and rigidity to minimize inversions to an acceptable level and the resilience to return the hybrid ribs to their original shape without experiencing permanent distortion. 
     Another object of the present invention is to provide ribs for a compact, folding umbrella which incorporates a hybrid structure comprised of first and second interconnected components which are respectively formed of aluminum of a size, shape and thickness to provide composite ribs having the strength and rigidity needed to minimize inversions and fiberglass of a size and shape needed to provide the elasticity necessary to return the rib back to its original shape and state without experiencing permanent distortion due to bending. 
     SUMMARY 
     In one preferred embodiment a compact, multiple fold umbrella is comprised of a support frame incorporating a hybrid rib typically located intermediate a main rib and a rear or outermost rib. The hybrid rib is formed of multiple sections composed of first and second materials which respectively provide the desired structural strength to reduce inversions of the umbrella to an acceptable minimum and provide the hybrid rib with the desired resiliency and flexibility to return the hybrid rib from a bent shape to its original unstressed shape and thereby prevent permanent damage to the hybrid rib as well as adjoining frame elements of the umbrella. The thicknesses of the multiple sections and the relative sizes of the sections also significantly contribute to the capability of the hybrid rib to achieve the desired objectives of a compact, small, folding umbrella of reduced weight, and the ability to prevent permanent damage to the frame due to inversion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above as well as other objects and advantages of the present invention will become apparent upon reading the accompanying description and drawings in which: 
         FIG. 1  is a perspective view of a folded umbrella frame of the present invention showing the frame in the unfolded, open position. 
         FIG. 2  is a side profile view of a rib design according to the invention and employed in the frame shown in  FIG. 1 . 
         FIG. 3  is a top view of the rib design shown in  FIG. 2 . 
         FIG. 4  is a bottom view of the rib design shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a simplified view showing the principal elements of a compact, light-weight, foldable umbrella  10  embodying the principles of the present invention and with the rain-protecting fabric (not shown) removed to facilitate a clear understanding of the invention and its novel features and advantages. 
     The foldable umbrella  10  is comprised of a main shaft  12 . The lower end  12   a  is typically provided with a handle ( 12   b ) at the lower end and configured to facilitate gripping of the umbrella during use. An annular cap  14  is provided at the top end of shaft  12 . Shaft  12  extends through a hollow, annular collar  16 , typically referred to as a runner, which is slidable along main shaft  12 . A first main stretcher  18  has its left-hand end  18   a  pivotally coupled to cap  14 . A support stretcher  20  has its left-hand end  21   a  pivotally coupled to slidable collar  16  and has its opposite end  20   b  pivotally coupled to a mid-point  18   b  of main stretcher  18 . The right-hand end  18   c  of main stretcher  18  is pivotally coupled to the left-hand end  22   a  of a second main stretcher forming a hybrid rib  22 . The left-hand end  24   a  of secondary support stretcher  24  is pivotally coupled at a point inward from end  20   b  of support stretcher  20  and the fight-hand end  24   b  of secondary support stretcher  24  is pivotally coupled to the left-hand  22   a  end of hybrid rib  22 . The right-hand end  22   b  of rib  22  is pivotally coupled to rear rib  26  at a point located inward from end  26   a  of rear rib  26 . A flexible member  28  has its left-hand end  28   a  pivotally coupled to main stretcher  18  at a point inward from the right-hand end of main stretcher  18  and its right-hand end  28   b  pivotally coupled to end  26   a  of rear rib  26 . When the umbrella frame is opened, angle  Ø 1    formed between elements  18  and  22  increases, pulling element  28  to the left relative to the hybrid rib  22 , causing flexible member  28  to rotate counter-clockwise about a pivot pin coupling elements  22  and  26 , thereby increasing the angle Ø 2  between hybrid rib  22  and rib  26  and moving the umbrella frame  10  to the fully open position. 
     In one embodiment, umbrella  10  is folded, i.e., collapsed, by moving collar  16  downward relative to shaft  12  in the direction of arrow A and against the opening force of a spring (not shown for purposes of simplicity) contained within shaft  12  and thereby causing all of the stretchers, supports and ribs to move next to and substantially in parallel with the longitudinal central axis of shaft  12 , providing an umbrella which is compact and easy to handle and store. The angle  01  reduces toward zero, causing flexible member  26  to move to the right relative to hybrid rib  22 , rotating element  26  clockwise about its pivot pin and reducing  02  to zero to collapse the umbrella frame. 
     In another embodiment, umbrella  10  is folded by releasing a locking mechanism (not shown) arranged between collar  16  and shaft  12 , enabling collar  16  to move downward relative to shaft  12  in the direction of arrow A under the opening force of a spring (not shown for purposes of simplicity) contained within shaft  12  and thereby causing all of the stretchers, supports and ribs to move next to and substantially in parallel with the longitudinal central axis of shaft  12 , likewise providing an umbrella which is compact and easy to handle and store. 
     Both of the embodiments described above undergo multiple folds, namely a first fold between main shaft  12  and main support stretcher  18 , a second fold between main support stretcher  18  and rib  22  and a third fold between rib  22  and rear rib  26 , opposing ends of rib  22  being joined to adjacent elements to form the two folds of the umbrella. This design significantly reduces the length of the umbrella frame, and hence the umbrella, when in the collapsed condition, as compared with folding umbrellas experiencing only a single fold. The reduced length of the multiple-fold umbrella comes at the expense of requiring more frame components which must be designed to provide structural strength equivalent to single-fold umbrellas and without significantly increasing the weight of the umbrella frame. 
     To provide a foldable umbrella which is both light-weight and compact, the stretchers, supports and ribs are designed to at least partially nest into or be nested by one of the neighboring components that comprise the support frame, it being understood that the protective fabric is secured to the frame at limited points thereof and surrounds the frame when in the collapsed condition. 
     The stretchers and supports and portions of the ribs which comprise the umbrella frame have a substantially U-shaped configuration which serves the dual functions of increasing the structural strength through the use of the U-shaped portions and facilitating nesting and/or compactness of these components when in the folded condition. 
     It is also important to select the thicknesses of these components in order to provide a folding umbrella that is both light-weight and compact, while providing the necessary structural strength and flexibility to prevent forces, such as wind, which invert the open umbrella, from subjecting the umbrella frame from experiencing permanent distortion and damage. 
     The materials typically employed in folding umbrellas, and their advantages and disadvantages, are: 
     ALUMINUM: Although aluminum is a light-weight metal and is capable of producing inexpensive frame components, an all-aluminum rib has the disadvantage of being easily distorted when subjected to bending and not return to is original shape when the force causing bending is removed, thereby causing permanent damage to all aluminum components. 
     STEEL: Like aluminum, an all-steel rib will remain distorted after the umbrella inverts, since steel will remain distorted if the rib is bent due to wind force. Steel has the disadvantage of being significantly heavier than aluminum and is less resistant to corrosion than aluminum. 
     PLASTIC: All-plastic ribs offer some flexibility, but lack the strength of metal alloys. All-plastic ribs or partial plastic ribs are more likely to break or snap when stressed by wind force. 
     CARBON FIBER: Carbon fiber is made of thin strands of carbon, while fiberglass is made of glass textile fiber. Although ribs composed entirely or partially of carbon fiber is more resilient than plastic, carbon fiber is much stiffer and less flexible than fiberglass. A rib fully or partially composed of carbon fiber lacks the flexibility of the Aluminum/Fiberglass combination rib. In addition, carbon fiber costs are substantially higher to produce than fiberglass. 
     Rib  22  is the structural element which is the most vulnerable to being permanently damaged due to inversion. The present invention replaces a conventional rib, typically formed of a light-weight metal, with a hybrid rib  22  that has been designed to prevent permanent damage due to inversion. The hybrid rib  22 , shown best in  FIGS. 2-4 , is composed of three components  22 - 1 ,  22 - 2  and  22 - 3 . Components  22 - 1  and  22 - 3  define opposing end sections of the hybrid rib and are formed of a suitable aluminum alloy. Component  22 - 2  is an intermediate section formed of fiber glass reinforced plastic. The aluminum sections  22 - 1  and  22 - 3  are significantly lighter in weight than steel and more resistant to corrosion. Fiberglass reinforced plastic section  22 - 2  provides the desired flexibility without experiencing the breakage occurring when using ordinary plastic. Although ribs composed entirely or partially of carbon fiber are more resilient than plastic, carbon fiber is much stiffer and less flexible than fiberglass. A rib fully or partially composed of carbon fiber lacks the flexibility of the hybrid rib of the present invention. In addition, the cost of producing carbon fiber is substantially greater than the cost of producing fiberglass reinforced plastic. 
     Section  22 - 2  is comprised of a fiber glass reinforced plastic having fiber glass fibers embedded in the plastic material. Section  22 - 2 , in one embodiment, preferably has a rectangular cross-section with its thickness being less than its width as will be described below in greater detail. 
     Sections  22 - 1  and  22 - 3  are hollow, elongated sections with U-shaped having wall thicknesses “th” set forth in paragraph [0039]. The free end of section  22 - 1  defines the left-hand end of hybrid rib  22  and tapers from a width W 1  over the major portion of its length to a narrow end having a width W 2 . A first pair of openings  01  cooperates with openings (not shown) in secondary support stretcher  24  to receive a pivot pin (not shown). A second pair of openings  02  cooperates with openings (not shown) in main support stretcher  18  to receive a pivot pin (not shown). The pivot pins (not shown) inserted in the above-mentioned cooperating openings enable swinging movement of the connected elements relative to one another. Section  22 - 3  is provided with a pair of openings  03  that cooperate with openings (not shown) in rear rib  26 . A pivot pin is inserted in the cooperating openings of elements  22 - 3  and  26  to enable swingable movement of the connected elements  22 ,  26  relative to one another. An end portion of rear rib can be seen to nest into section  22 - 3  when the umbrella is open. 
     The left-hand end of section  22 - 2  extends into the right-hand end of section  22 - 1  and the right-hand end of section  22 - 2  extends into the left-hand end of section  22 - 3 . Sections  22 - 1  through  22 - 3 , when joined, form a substantially straight, linear rib with the longitudinal axes of sections  22 - 1  through  22 - 3  lying substantially along a longitudinal common axis when rib is free from any bending forces. Section  22 - 1  has integral tabs T 1  through T 5  which wrap around section  22 - 2 , as shown in  FIG. 3 . A forming tool (not shown) having a tapered end is forced against one sidewall of section  22 - 1  to form a small depression D 1  in the sidewall, which in turn, is pressed into an adjacent surface of section  22 - 2 , firmly securing sections  22 - 1  and  22 - 2  to one another. Tabs T 1 -T 5  and the depression D 1  in section  22 - 1  extending into section  22 - 2 , cooperate to firmly secure sections  22 - 1  and  22 - 2  to one another and further prevent longitudinal movement of sections  22 - 1  and  22 - 2  relative to one another. The integral tabs T 6  and T 7  of section  22 - 3  wrap around section  22 - 2 . Depressions D 2  and D 3 , formed by the aforesaid forming tool, both pierce into section  22 - 2 . Tabs T 6 -T 7  and depressions D 2 , D 3  cooperate to firmly secure sections  22 - 2  and  22 - 3  to one another and further prevent longitudinal movement of sections  22 - 2  and  22 - 3  relative to one another. 
     Rear rib  26  is preferably formed of an aluminum section  26 - 1 , shown in dotted fashion in  FIGS. 2-4 , and a flexible fiberglass section  26 - 2 . 
     In order to obtain optimum balance between the rigidity and structural strength of hybrid rib  22  to maintain inversions to an acceptable level and the flexibility and resilience to prevent permanent damage of the umbrella frame due to inversions, section  22 - 1  is formed of an aluminum alloy having a thickness TH preferably in the range of from 0.4&lt;TH&lt;0.9 mm and most preferably in the range of from 0.5 to 0.7 mm. The thickness of elements  18  and  20  are also preferably in the range of from 0.4&lt;TH&lt;0.9 mm and most preferably in the range of from 0.5 to 0.7 mm. The thickness range of section  22 - 3  may deviate from the most preferred thickness range set forth for section  22 - 1  and lie within the preferred thickness range. The length of section  22 - 3  is preferably less than the length of section  22 - 1 . 
     The width W 3  of rectangular-shaped, fiberglass section  22 - 2  is less than the width W 1  of the section  22 - 1  to enable the section  22 - 2  to fit into the right-hand end of section  22 - 1 . The thickness TH 1  of section  22 - 1  is less than the width W 3  to provide greater flexibility and resilience to forces which act on section  22 - 2  in a direction substantially parallel to the central, longitudinal axis of the main shaft direction and which cause inversion to enhance the ability of section  22 - 2  to resume its original shape when the inversion forces are removed. The ratio of thickness TH 1  to width W 3  of rectangular-shaped, fiberglass section is preferably in the range of from TH 1 =50% W 3  to TH 1 =75% W 3  and most preferably in the range of from TH 1 =60%W 3  to TH 1 =70% W 3 . The length of section  22 - 3  relative to section  22 - 1  is preferably in the range of from 40% to 85% of the length of section  22 - 1  and most preferably in the range of from 50% to 60% of the length of section  22 - 1 . In either case the length of section  22 - 3  is less than the length of section  22 - 1 . 
     Section  22 - 1  provides the integrity needed to minimize inversion of the umbrella to an acceptable level when fully extended. Fiber glass reinforced plastic section  22 - 2  provides the flexibility to return the rib  22  back to its original shape when inversion forces are removed and thereby prevents rib  22  from experiencing distortion and permanent damage in the event of an inversion and further absorbs a significant amount of the force that would otherwise be transferred to the main stretcher  18  and rear rib  26  by an all-aluminum rib. Section  22 - 3  attaches the composite rib  22  to the adjoining last or rear rib  26 . Hybrid rib  22  thus protects elements  18 ,  20 ,  24  and  26  from permanent damage by absorbing the forces experienced due to inversion.