Patent Publication Number: US-2012031446-A1

Title: Umbrella, umbrella frame and rib therefor

Description:
FIELD 
     This invention relates to an umbrella, an umbrella frame and a rib for an umbrella, and is applicable to all types of umbrellas, parasols and the like, including collapsible and non-collapsible variants. 
     BACKGROUND 
     The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art. 
     There are known a number of umbrella designs. These are used to protect a user from rain, sun and and/or wind. A conventional umbrella has a rigid central shaft and a plurality of ribs or spokes attached to the top of the central shaft. Supporting struts or connecting ribs connect the ribs or spokes to a slider on the central shaft. The frame of the umbrella is thus movable between open and closed configurations, but each rib or spoke is of fixed dimensions, and is usually of one piece construction. 
     Other umbrella designs are described as compact or multiple fold, and sometimes as collapsible. They have ribs that have a number of elements pivotally connected together, and usually the central shaft has two or more elements that telescope together, so that when collapsed or folded, the umbrella is smaller and more compact. 
     For all these known umbrella designs, the ends of the ribs are generally perpendicular to the periphery of the canopy and are exposed. Even if the ribs are rounded or otherwise provided with protective elements, they still can be a nuisance to others and a danger to people&#39;s eyes. 
     U.S. Pat. Nos. 5,394,896 and 5,305,771 to Peter Wilk disclose a frame for an umbrella that has ends of the ribs connected together by curved elements, intended to eliminate the problem of the tips of the ribs protruding beyond the canopy. However, this patent fails to recognize that in a collapsed or folded configuration, the effective radius of the ribs is increased beyond the effective radius in the open configuration. This proposal does not have the edge or periphery of the canopy attached to the frame at any point. 
     A more recent proposal is disclosed in published PCT application WO 2005/048765. It provides a complex arrangement, in which the ribs have rods sliding within tubes, to actuate force spreading compartments at the end is of the ribs. 
     SUMMARY 
     The following introduction is intended to introduce the reader to this specification but not to define any invention. One or more inventions may reside in a combination or sub-combination of the apparatus elements or method steps described below or in other parts of this document. The inventor does not waive or disclaim his rights to any invention or inventions disclosed in this specification merely by not describing such other invention or inventions in the claims. 
     In accordance with a one aspect of the present invention, there is provided a frame for an umbrella for supporting a canopy, the frame comprising: a main shaft; a plurality of ribs connected to the main shaft, each rib including a pair of outer rib elements, with an outer end of the each outer rib element being connected to the free end of the outer rib element of an adjacent rib, and being adapted to be attached to the periphery of the umbrella canopy. 
     In accordance with a another aspect of the present invention, there is provided frame for an umbrella, the frame comprising a main shaft, a plurality of ribs pivotally connected to the main shaft, each rib being of adjustable length, and each rib including a pair of outer rib elements, that are flexible, whereby in use, the outer rib elements in a closed configuration, extend generally straight and aligned with the main shaft, and in an open configuration, are flexed so that outer ends thereof extends generally circumferentially. 
     In accordance with a another aspect of the present invention, there is provided A foldable umbrella comprising: a canopy; a main shaft; a plurality of ribs pivotally attached to the main shaft, each rib comprising at least two rib elements pivotally attached to one another, to enable the umbrella to fold to a compact closed configuration, and each rib further including a pair of outer rib elements, that extend generally straight and aligned with the main shaft in the closed configuration, and in an open configuration have outer ends extending generally circumferentially with respect to the canopy. 
     In accordance with a further aspect of the present invention, there is provided umbrella comprising: a canopy; a main shaft; a plurality of ribs pivotally attached to the main shaft, each rib being of adjustable length and including a pair of outer rib elements, wherein the outer rib elements are flexible and normally adopt a straight configuration aligned with the main shaft in a closed position of the umbrella, and in an open position of the umbrella, flex so that outer ends of the outer rib elements extend generally circumferentially with respect to the canopy. 
     The present invention also provides a rib structure for an umbrella or the like, comprising an inner rib element, and a pair of outer rib elements, that are flexible, for adopting a straight configuration in a closed configuration of an umbrella and being capable of flexing for an open position of an umbrella. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings which show, by way of example, the present invention and in which: 
         FIG. 1  is a perspective view of a first embodiment of an umbrella according to the present invention, in an open configuration; 
         FIG. 2  is a perspective view, similar to  FIG. 1 , on an expanded scale; 
         FIG. 3A  is a view of the first embodiment of the umbrella in a closed configuration; 
         FIGS. 3B-3D  are perspectives view of the first embodiment showing progressive opening of the umbrella; 
         FIGS. 4A and 4B  are perspective views of the first embodiment; 
         FIG. 4C  is a view of part of the frame of the first embodiment in a closed position, and  FIG. 4D  and  FIG. 4E  show the frame moving to the open position; 
         FIGS. 5A ,  5 B,  5 C,  5 D and  5 E;  6 A and  6 B;  7 A and  7 B;  8 A and  8 B; and  9 A,  9 B,  9 C and  9 D show variants of outer rib elements; 
         FIG. 10  shows a first variant of a joint between outer rib elements; 
         FIG. 11A  and  FIG. 11B  show a second variant of a joint between outer rib elements; 
         FIG. 12A  a shows a perspective view of a second embodiment of an umbrella according to the present invention; 
         FIG. 12B  shows a side view of the second embodiment; 
         FIG. 12C  shows a side view of the second embodiment in a partially closed position; 
         FIGS. 12D and 12E  show side views of the second embodiment in the closed position. 
     
    
    
     DETAILED DESCRIPTION 
     Various apparatuses or methods will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover apparatuses or methods that are not described below. The claimed inventions are not limited to apparatuses or methods having all of the features of any one apparatus or method described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or method described below is not an embodiment of any claimed invention. The applicants, inventors and owners reserve all rights in any invention disclosed in an apparatus or method described below that is not claimed in this document and do not abandon, disclaim or dedicate to the public any such invention by its disclosure in this document. 
     Reference will first be made to  FIGS. 1-4  of the drawings, which show a first embodiment of the present invention. This first embodiment is designated by the reference  10 , and is shown with a frame  40  having eight equally spaced ribs  12 . The number of ribs may be varied, and for example, the umbrella  10  could have ten, twelve, fourteen, sixteen, eighteen, twenty or more ribs, including an odd number of ribs; it is also conceivable that the umbrella  10  may have less than eight ribs. As detailed below, the umbrella of the present invention has outer rib elements, that are straight in a closed configuration, but flex and are curved in a closed configuration; consequently, the effective radius or length of the ribs in the closed configuration is increased compared to their length in the open configuration. The smaller the number of ribs, the greater is this effect. 
     The first embodiment of  FIGS. 1-4  is for an umbrella at  10  that would otherwise have ribs  12  that are of constant length. This first embodiment provides ribs  12  of variable or adjustable length, to accommodate this effect of the varying of the effective radius of the outer rib elements. A second embodiment, described below in relation to  FIGS. 12A-12E , provides a folding or collapsible rib structure. It has been realized that when such an umbrella frame is folded or collapsed it inherently provides slack in the canopy, they can be used to accommodate the effective increase in length of the ribs  12 . 
     It is also to be understood that while the present invention is described in relation to umbrellas for individual use, it is applicable to any type of umbrella, parasol, sunshade, or similar canopy. It is applicable to umbrellas of any size, including beach umbrellas, golf umbrellas, patio umbrellas, etc. Further, it is applicable to asymmetric umbrellas having ribs of different lengths. For example as disclosed in published PCT application WO2006/132525. 
     Each rib  12  has an inner rib element  14  and a middle rib element  16 , that are slidably connected. As shown, the inner rib element  14  may be a rod, and the middle rib element  16  may be a tube. It may be preferable to reverse this arrangement, with the inner rib element  14  configured as a tube, and the middle rib element  16  configured as a rod. Any other suitable sliding arrangement can be used. 
     The middle rib element  16  is connected to a pair of outer rib elements  18 . As detailed below, the outer end of each rib element  16  is either connected to the outer end of a rib element of an adjacent rib  12 , or is connected to a canopy  20  of the umbrella term, so as to be maintained close to or adjacent the outer end of the rib element of the adjacent rib  12 . In some embodiments, in the open configuration the ends of the outer rib elements  18  of adjacent ribs  12  may be spaced apart. A variety of arrangements can be provided for the outer ends of the outer rib elements  18 , as detailed below. 
     Each rib  12  has a primary support rib  22 , pivotally connected to its middle rib element  16  at  24 , and to a first slider  26 . A secondary support rib  28  is pivotally connected to the primary support rib  22  at  30 , and to a second slider  32 . 
     In known manner, locking mechanisms can be provided for holding the umbrella frame, indicated generally by the reference  38 , at desired positions. Such mechanisms can include spring loaded protrusions extending out through slots in the main shaft  42 . 
       FIGS. 1 and 2  show the umbrella  10  and its frame  40  in a generally open configuration. Reference will now be made to  FIGS. 3A-3D  and to  FIGS. 4A-4E , which show the frame  40  as it is progressively opened. 
     In  FIG. 3A , the frame  40  is shown in a closed position, with the ribs  12  close to the main shaft  42 . As shown, the outer rib elements  12  extend generally downwardly and parallel to one another. The effect of this is to give an overall effective radius for the ribs  12  as indicated at  44 . To initiate opening of the umbrella term, a user grasps a handle  46  at the bottom of the main shaft  42 , and the first slider  26 . In known manner, the user may first have to release a locking member or catch, used to retain the first slider  26  and thus the frame  40  generally in the closed configuration. 
     As the first slider  26  is displaced upwardly along the shaft  42 , the ribs  12  are displaced outwardly as shown in  FIG. 3B . Simultaneously, The primary support Ribs  22  and their connection  24  to the middle rib elements  16  are displaced outwardly. In turn, the connections  30  for the secondary support ribs  28  are displaced radially outwards away from the main shaft  42 . Consequently, while the second slider  32  is displaced upwards along the main shaft  42 , the first and second sliders  26 ,  32  move closer together. 
     The spring  34  functions to resist upward movement of the second slider  32 . To ensure that too greater force is not required to open the umbrella  10 , it may be desirable to give the spring  34  a low spring constant. The resistance to movement of the second slider  32  by the spring  34  promotes displacement of the connections  30  outwards. In turn, this causes the middle rib elements  16  to slide along the inner rib elements  14 , tending to expand the length of the ribs  12 . 
     It may be desirable to ensure that this sliding motion of the middle elements  16  occurs before the frame  40  reaches or is close to the open configuration. As the frame  40  reaches the open configuration, the ribs  12  are flexed, and this may make sliding motion between the inner and middle rib elements  14 ,  16  more difficult and subject to more friction. Therefore, it may be preferable to ensure that all or most of this sliding action occurs before the ribs  12  are flexed and stressed by the canopy  20 . But this purpose, as detailed in published PCT application WO 2005/048765, a mechanism may be provided that halts the motion of the second slider  32  at a certain point, so that continued motion of the first slider  26  causes the middle rib elements  16  to slide radially outwards to the maximum desired extent. Further motion of the first slider  26  then releases the second slider  32  permitting both slider elements  26 ,  32  to reach a final open configurations shown in  FIG. 3D . For this purpose, the first slider  26  has a lower collar  26   a  and an upper collar  26   b . the lower collar  26   a  is for gripping by a user, while the upper collar  26   b  abuts the second slider  32 , to effect the action detailed above. 
       FIG. 3D  shows the frame  40  in the fully open position. The canopy  20  is indicated in outline at  50 . It has an effective radius at  52 , which as shown also at  52  in  FIG. 3A  is less than the effective radius that the ribs  12  have in the closed position, indicated at  44 . 
       FIGS. 4A-4E  also show the effect of the varying rib length. As indicated in  FIGS. 4A and 4D , at the start of the opening of the umbrella, the middle rib elements  16  have only extended slightly along the rib elements  14 , as indicated at  56 . This is only slightly larger than the initial spacing, indicated at  58  in  FIG. 4C . When the umbrella is fully open, the middle rib elements  16  have slid further along the inner rib elements  14 , so as to give a spacing indicated at  60 . As mentioned above, the spacing is selected to accommodate the effective change in radius as the outer rib elements  18  bent from the straight configurations shown in  FIGS. 3A and 4C , to the fully open configuration shown, for example, in  FIGS. 3D and 4E . 
     This effective change in radius will depend on various factors, including the number of ribs  12 , and characteristics of the outer rib elements  18 . As detailed below, the outer rib elements  18  can have a number of different profiles or cross sections. Moreover, the outer rib elements  18  can have cross sections that vary along the length thereof, so as to give different bending characteristics at different points. A simple analysis assumes that, in the open configuration, a pair of adjacent and connected outer rib elements  18  form part of a circle, effectively slightly more than a semicircle, that is tangential with the middle rib elements  16 ; this analysis is further done just in two dimensions, and overlooks the more complex three-dimensional domed shape of an umbrella. On this analysis, the difference in radius between the open and close configurations, measured as a percentage of the radius in the open configuration is: 22.8% for 8 ribs; 18.6% for 10 ribs; and 14.9% for 12 ribs, and will be less for a larger number of ribs, e.g. 14, 16, 18 or 20 ribs. 
     Taking approximate sizes for the radius of conventional umbrellas of 76 cm (30 inches) for a golf umbrella, and 57 cm (22½ inches) for a compact folding or collapsible umbrella, one can calculate numerical values for the change in radius. For the golf umbrella, the values are: 17.3 cm for 8 ribs; 14.1 cm for 10 ribs; and 11.3 cm for 12 ribs. For the compact, folding umbrella, the values are: 13 cm for 8 ribs; 10.6 cm for 10 ribs; and 8.5 cm for 12 ribs. While the mechanism shown in  FIGS. 1-4  is schematic, it will be understood that the relative proportions of the different elements can be varied to give the values indicated above for the golf umbrella; it will further be understood that this general principle applies to any umbrella that otherwise would have fixed for one piece ribs. As detailed below, for the folding or collapsible umbrella, dimensions can be chosen for the mechanism, so that it inherently accommodates the change in radius. 
     Reference will now be made to  FIGS. 5-9 , which show variants for the outer rib elements  18 , here distinguished from one another by use of suffixes a, b, etc. 
       FIG. 5A  shows a middle rib element  16 , formed as a tube, slidably engaging an inner rib element  14 , shown in part as a rod. As noted above, alternatively the middle rib element  16  could slide within the inner rib element  14 , with the tube and rod arrangement reversed, or with any other suitable sliding configuration.  FIGS. 5A and 5B  show outer rib elements  18   a  having a rectangular cross-section. In known manner, the second moment of area or the bending resistance is proportional to the width and the cube of the depth. Thus, if the depth is three times the width, then, as shown in  FIG. 5C , the second moment of the area about axis  62  is nine times greater than that about axis  64 . Arrows  66 ,  68  indicate schematically the larger bending deflection that will occur about the different axes for the same load or bending moment. 
     The profiles of the rib elements  18  may be selected to give desired bending characteristics and strength. To withstand wind loads, the outer rib elements  18  can be given significant depth in a direction generally perpendicular to the canopy  20  (recognizing that the canopy  20  is not a simple plane surface, but rather a complex three-dimensional curved surface). This is shown in  FIG. 5 . Simultaneously, to permit flexing of the outer rib elements  18  and opening of the frame  40 , without requiring undue force from a user, the outer rib elements  18  can be made relatively narrow in the horizontal direction of  FIG. 5C , to give a lower bending resistance the profile of  FIG. 5C  shows these characteristics. 
     Further, the outer rib elements  18  may not have a constant cross-section. For example, the cross-section can be varied to vary the second moment of area or bending resistance about one or both of the axes shown in  FIG. 5C . it may be desirable to maintain the bending resistance about axis  62  high and constant, to resist wind loads, while varying the bending resistance about the axis  64 , to ensure that the outer rib elements  18  adopt a desire profile. 
     For example, the horizontal width (horizontal dimension in  FIG. 5C ) may taper from a large dimension at the inner end of each outer rim element  18  to a smaller dimension at the outer end thereof, so that the outer end portion is more flexible. The depth may be held constant or may also taper similarly from the inner end to the outer end. An analogy can be made with fishing rods the commonly taper from the handle to the end of the rod. It will be understood that even if the depth is held constant, tapering the width will affect both the second moments of area; however the second moment or area about the axis  64  (that affects deflection in the direction of arrow  66 ) will be affected more than the other second moment of area about axis  62 . 
       FIGS. 6A and 6B  show an alternative profile for the outer rib elements  18   b , which is circular. Here, to give varying bending characteristics the diameter of the cross-section may be varied. Further, to vary the bending characteristics about the different axes, the cross-section can vary from circular at different points along the rib elements  18   b.    
       FIGS. 7A and 7B  show an elliptical cross-section for the outer rib elements  18   c . Again, the dimensions of this cross-section can be varied to give desired bending characteristics along the length of the outer rib elements  18 . The relative dimensions of the major and minor axes of the elliptical cross-section can be varied, to vary the bending characteristics about the different axes independently. 
       FIGS. 8A and 8B  show a square cross-section for the outer rib elements  18 . Again, this profile can be varied along the length of the outer rib elements  18 , to give desired characteristics. 
       FIGS. 9A and 9B  show a variant in which the outer rib elements  18   a , as in  FIG. 5C , have different second moments of area about two axes. Here, the outer rib elements  18   a  are secured to the middle rib element  16 , so that their axes  88  are inclined at an angle relative to one another. As viewed in  FIG. 9A , the axes  88  at an angle to the horizontal. This is used to control the shape of the canopy  20 . As shown in  FIG. 9D , a shallow V-shape appears when the canopy  20  is viewed generally along the top of the canopy, i.e. directly at the periphery of the canopy. As shown at  70   a , outer ends  70  of the outer rib elements  18  meet at a shallow angle. If the two moments of area about the axes  62 ,  64  are adjusted so that the rib elements can bend relatively easily in response to a small load in the direction of arrow  66 , but are stiff in response in the direction of arrow  68 , then it should be possible to achieve this shape with little deflection in the direction of arrow  68 , i.e. generally perpendicularly to the canopy. 
       FIG. 10  shows one connection between outer ends  70  of the outer rib elements  18 , in the form of a living hinge  72 . The living hinge  72  may be integrally formed with or attached to the outer ends  70 . Living hinge  72  includes an opening  74  to permit the hinge  72  to be attached by sewing to the edge of the canopy  20 . 
       FIG. 11A and 11B  show a pivot or hinge  76 , including a pivot element  78 , that can be in the form of a rivet. As shown in  FIG. 11B , the ends up the outer rib elements  18 , here indicated at  70   b  can be shaped to overlap and provide a constant thickness at the hinge  76 . By providing an opening  79  through the pivot element  78 , the hinge  76  may be attached to the periphery of the canopy by sewing. The pivot element may be strong enough to transmit bending loads between the ends  70 , so as to maintain them aligned in a torsional sense, ie with respect to torsional loads about an axis that is horizontal and in the plane of  FIG. 11B , and also in response to bending loads about an axis perpendicular to the plane of  FIG. 11B . The pivot connection can also limit the angular extent of the opening of the ends  70 , to that shown in  FIG. 11 . 
     It will also be understood that various other mounting and connection arrangements can be provided for the ends  70  of the outer rib elements  18 . Instead of adjacent ends  70  being connected together, each end  70  could be connected, e.g. by sewing in known manner, to the periphery of the canopy  20 , and may be spaced from one another. Another alternative is to provide pockets in the canopy to receive the ends  70  of the rib elements  18 . 
     As shown in  FIG. 5C , the outer rib elements  18 , may have a relatively narrow width, to enable them to flex freely, so that no great force is required to open the umbrella. However, the outer rib elements  18  can be attached to the canopy  20 , so that the canopy  20  serves a structural function and limits the flexing of the rib elements  18 .  FIG. 5D  shows how the rib elements  18  may be attached at various points, indicated that  80  to the canopy  20 . As indicated by the arrow  82 , if a radial force is applied where the rib elements  18  join, this tends to force the rib elements  18  to bow outwards, as indicated at  84 . Due to the connections at  80 , this movement is resisted and a portion of the canopy  20 , indicated that  86 , between the rib elements  18  is put into tension. Thus, the rib elements  18  will appear to be much stiffer, and this overall arrangement can be designed to provide the necessary tension in the canopy. 
     As shown in  FIG. 5D , it is possible for the canopy  20  to be provided as a number of separate canopy elements  90  joined along edges  92  that follow the ribs  12  and the outer rib elements  18 . As shown in  FIG. 5E , it is possible for joints between the canopy elements  90 , to be formed to provide elongate channels  94 , that may be continuous or in segments into which the outer rib elements  18  are inserted. The canopy elements are sewn together or otherwise joined at  96 . This again will enable the canopy  20  to provide a structural function and to prevent excessive flexing of the outer rib elements  18 . 
     To accentuate the design of the frame and umbrella, different patterns or colours can be applied to the individual canopy elements  90 , to emphasize that, unlike conventional umbrellas, these are not simple triangular elements. These canopy elements may comprise central canopy elements  90   a , and peripheral canopy elements  90   b , the later being indicated by their outer periphery. 
     Further to accentuate the shape enabled by the new design, the canopy elements indicated at  90   b  can be omitted, or can be replaced with smaller canopy elements whose edges are set back from the main periphery of the canopy. Examples are indicated at  90   c, d, e , and  f , showing both different sizes and different edge peripheries (it will be understood that, while 
       FIG. 5D  shows a number of variant designs, generally just one design would be used for the whole umbrella, although it is possible to provide any combination of the different designs around the umbrella). In this case, at least part of the rib elements can be enclosed in pockets formed from edges of the canopy elements indicated at  90   b . As noted above, tension in the canopy elements  90   a  will then effectively provide added rigidity in response to loads, eg impacts, at the edge of the canopy generally tending to deflect the canopy inwards towards the main shaft of the umbrella. 
     Where the canopy elements  90   b  are omitted entirely, indicated at  90   g , or are quite small, the umbrella then presents a multi-lobed appearance resembling a flower. 
     Reference will now be made to  FIGS. 12A-12C , which show a collapsible or foldable umbrella according to a second embodiment of the present invention. Similar reference numerals are used as for the first embodiment, but with the suffix  100  added, for many references. Thus, the second embodiment is denoted by the reference  110 , has a frame  140  and includes a main shaft  142  with the ribs  112  pivotally attached to the upper end of the shaft  142 . 
     A first slider  126  is spaced from a second slider  132  by a spring  128 , that is relatively strong and is used to effect opening of the umbrella  110 . The ribs  112  have inner rib elements  114 , that are pivotally attached the second slider  132 . Actuation links  124  are pivotally connected to the first slider  126  and the inner rib elements  114 . A comparison of  FIG. 12B  and  FIG. 12C  shows that as the umbrella  110  moves from the closed position (the partially closed position being shown in  FIG. 12C ) to the open position of  FIG. 12B , the spring  128  is able to expand. This expansion drives the umbrella from the closed to the open position. 
     Each inner rib element  114  is pivotally connected to a first connecting rib  122 , whose other end is pivotally connected to the top of the main shaft  142 . A middle rib element  116  is pivotally connected to a respective inner rib element  114 , at a location spaced from the inner and thereof. The inner end of each middle rib element  116  is pivotally connected to a second connecting rib  130 , whose other end is pivotally connected to the first connecting rib  122 , as shown. Each middle rib element  116 , as for the first embodiment, is connected to a pair of outer rib elements  118 . Each outer rib element  118  has a tip or end that is connected to or otherwise maintained close to the tip or end of an outer rib element  118  of an adjacent rib  112 . The various connection and mounting arrangements for the ends of ribs discussed in relation to  FIGS. 5-11  are applicable to this second embodiment. 
     As  FIG. 12B  and  FIG. 12C  show, the Spring  128  expands and drives the sliders  126 ,  132  apart. The actuation links  124  pull the inner rib elements  114  down from position close to the main shaft  142 , to the extended position shown in  FIG. 12B . As the inner rib elements  114  move to the extended, open position, they displace ends of the first connecting ribs  122  away from the main shaft  142 , effectively pulling the second slider  132  towards the top of the main shaft  142 ; in known manner, at the top of the main shaft  142 , there is an element  144 , to which the first connecting ribs  122  are pivotally connected. 
     As the inner rib elements  114  and the first connecting ribs  122  move towards the extended position in  FIG. 12B , the second connecting ribs  130  cause the outer rib elements  118  to pivot and extend outwardly. 
     Between the top of the second slider  132  and the top element  144 , there is a spring  134 , with a relatively low spring constant. It serves to cushion motion of the second slider as it moves to the extended position of  FIG. 12B . 
     Conventionally, a canopy or a cover  120 , for such a collapsible or foldable umbrella, is attached to elements of the umbrella frame  140 , to assist the canopy  120  in being maintained in a desired position and folding neatly. Thus, the canopy  120  may be attached to the ribs  112  at various locations along the middle and outer rib elements  116  and  118 . Further, as indicated at  148 , a connecting link for each rib  112 , often a length of thread of like, is provided between the first connecting rib  122  and the canopy  120 . 
     Then, as shown in  FIG. 12C and 12D , as the umbrella collapses, the connecting links  148  pull inner portions of the canopy  20  downwards. 
     In the present invention, as for the first embodiment, the flexing of the outer rib elements  118  has the effect of increasing the radius, measured from the centre line axis of the main shaft  142 , from the extended or open position of  FIG. 12B  to the collapsed or folded position, shown in  FIG. 12D .  FIG. 12D  shows at  118   a  the extent of the outer ribs  118  in the open configuration, and at  118   b  at the greater extent of the outer ribs  118  in the folded or collapsed configuration. The consequence of this is that the fold shown at  120   a  for the cover, occurring in a conventional umbrella, may not occur or will be much less. Rather, as the umbrella moves to the folded configuration and the outer rib elements  118  straighten and extend, the canopy  120 , adjacent to the main shaft  142 , may extend somewhat as shown at  120   b.    
     Put another way, it has been realized that the characteristics of a folding or collapsible umbrella can be used to accommodate the extension of the outer rib elements  118  in the folded configuration. By suitably dimensioning the elements of the frame  140 , and choosing a suitable number of ribs  112 , it should be possible to accommodate all of this extension, without having to provide the sliding arrangement to give variable rib length, as in the first embodiment. 
     While the canopy  120  may still be attached to the middle and outer rib elements  116  and  118 , such attachment may need to accommodate relative movement between the canopy  120  and those rib elements. Thus, the canopy  120  will slide over the inner ends of the middle rib elements  116 , as the umbrella is opened and closed. The middle rib elements  116 , at least at their inner ends, may be provided with a finish or components providing for free sliding of the canopy  120 . Instead of the fixed connecting links  148 , these may be omitted, or replaced with links of a different length or elastic links. 
     For both embodiment of the present invention, these may be applied to asymmetric umbrellas, such as that described in WO2006/132525. In this case, the angles between the ribs  12  or  112  may be made unequal. The angles between the longer ribs can be smaller than the angles between the shorter ribs. These angles can be selected so that the effect of the outer rib elements giving an extension as they straighten out from their flexed shape can be more or less equalized for the different rib lengths. This property of unequal angles is another general aspect of the present invention applicable to the design of WO2006/132525, with conventional straight and independent ribs. 
     All the patents and patent applications disclosed herein are hereby incorporated by reference, without any admission that these documents constitute prior art. 
     While the invention has been described in various embodiments, various alternatives are possible, and modifications and additions may be made without departing from the scope of the present invention. For example, while the ends of pairs of outer rib elements from adjacent ribs may be connected together at their outer ends, this is not essential. Such a connection results in each outer rib element extending to a point that is half of the circumferential distance between the ribs. Alternatively, the outer rib elements can extend to a position that is less, e.g. only ⅓, ¼, or ⅕ of the the circumferential distance between the ribs. Then the ends of the outer rib elements would be individually attached or connected to the periphery of the canopy, e.g. by a sewn connection or by being received in a pocket of the canopy. As the outer elements still provide the flexing action and the effective change in radius detailed above, the mechanism of the frame may have to be dimensioned to accommodate this.