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BACKGROUND OF THE INVENTION 
   The present invention pertains to collapsible personal canopy shelters of typically light weight used as protection from wind or sun. In particular, the invention is such a shelter having unique frame hubs from which elongated frame elements extend radially and which allow both open and collapsed canopy conditions for ease of use, and portability. Such shelters are often referred to as “cabanas” and are employed typically in beach areas where sun and wind protection is often desired. 
   Similar cabana shelters are generally known in the prior art. For example, U.S. Pat. No. 4,355,650 to Beaudry discloses a typical prior art design for a personal shelter including a collapsible frame and a flexible cover. Beaudry discloses a frame formed of frame-like “bows” which pivot on a hub to alter the shape of an attached cover. However, the Beaudry hub design uses a cantilevered pivot design which is likely prone to failure and is susceptible to damage from sand during use. 
   SUMMARY OF THE INVENTION 
   The present invention is an improved cabana canopy and canopy hub. Generally “U” shaped canopy frame elements are attached at their ends to hubs of novel design. The novel hub enables coordinating the placement and movement of the canopy frame into open and collapsed conditions. The collapsed condition enables the canopy to be collapsed to a reduced-space geometry for more convenient portability and storage. The hub design uses large joint knuckle elements with relatively large bearing surface area to reduce susceptibility to damage from sand. 
   The hub consists of a hub body in which multiple joint knuckle elements are retained. Each joint knuckle is locationally captured yet allowed to rotate to allow movement of attached frame elements. Each joint knuckle is preferably shaped generally as a sphere and is received in a curved depression in the hub body. This geometry provides the large bearing surface desired in operation. Both the hub body and the joint knuckle are most advantageously formed of molded rigid structural plastic that, in combination with the joint knuckle design, provide a durable canopy hub and canopy for use in outdoor locations. 
   In one embodiment, each hub may be precombined with shortened stub arms secured to the joint knuckles. This assembly may then be advantageously combined with canopy frame elements, to form a finished canopy in a simplified process. In this embodiment, the stub arms preferably take the form of wooden dowels which slide into metal tubing frame elements of the canopy. 
   Additional elements and advantages of the invention are illustrated in the following description of preferred embodiments and the accompanying illustrations. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a  and  1   b  are, respectively, side and front views of a cabana canopy according to the invention in a configuration for use as a shelter, and including the present inventive canopy frame hubs. 
       FIGS. 2   a  and  2   b  are exploded isometric and side views, respectively, of the inventive cabana canopy frame hub. 
       FIG. 3  is a side view of the inventive hub including stub terminal end arms in an opened condition with the terminal end arms separated for an opened canopy. 
       FIG. 4  is a side view of the device of  FIG. 3  showing the stub terminal ends arms in a collapsed condition. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1   a  and  1   b  are, respectively, side and front views of a cabana canopy  100  according to the invention in a configuration for use as a personal shelter, and including two inventive canopy frame hubs  10 . The canopy  100  includes a cover  13  supported by generally “U” shaped frame elements  15  in the manner of many canopies in the prior art. The cover  13  is formed of a flexible sheet material such as cloth, canvas, rubberized cloth or plastic sheeting. The frame elements  15  are relatively rigid elongated structures, preferably formed of bent hollow metal tubing, such as aluminum tubing. In the prior art, bent or joined wood frame elements are also taught for such use. The frame elements  15  are dispersed over, and attached to, the cover  13  such that when separated, the frame elements  15  expand or stretch the cover  13  to create an open-faced shelter as shown in the figure. To provide a more compact collapsed configuration of the canopy, for portability and convenient storage, the frame elements  15  may all be gathered together in side-by-side stacked fashion, while the cover  13  is folded between. In the embodiment shown, there are five frame elements  15 , although other numbers may be similarly employed. At least two are necessary to stretch and open the cover  13 . 
   To enable the movement of the frame elements  15  between the separated condition (canopy as a shelter) and the collapsed condition (see FIG.  4 —for portability or storage), the frame elements  15  each have terminal ends  17  which are connected on opposite sides of the canopy to a respective hub  10 . Each hub  10  rotatably retains the frame element ends  17 , and guides their movement to, alternatively, smoothly open and stretch the cover  13 , or collapse the canopy. The terminal ends  17  may be integral with the frame elements  15  or attached extensions thereof of like or distinct material and construction. 
   The two canopy hubs  10  are preferably connected along a common axis by a rigid cross bar  19 . In this manner, each frame element&#39;s respective ends  17  are induced to move in coordinated fashion and prevent binding. This geometry is discussed in more detail below. The cross bar  19  need not provide complete torsional rigidity between the hubs  10  but rather limit angular displacement between the two sides. 
     FIGS. 2   a  and  2   b  are exploded isometric and side views, respectively, of a preferred embodiment of the inventive cabana canopy frame hub  10 . The hub  10  is formed of rigid hub side portions  24  which, when joined, capture and retain, in fixed relative positions, multiple rotational joint knuckles  22 . The joint knuckles  22  are retained in a common plane and each has a rotation axis perpendicular to the plane. Consequently, the axes are mutually parallel. This geometry enables the function of the joint knuckles  22  of positioning and coordinating the canopy frame ends  17  as discussed above. Each joint knuckle  22  in the figures is shown in a different angular orientation. 
   In the embodiment shown in  FIGS. 2   a,    2   b,  the hub  10  is preferably formed of two mating hub sides  24 . The hub sides  24  are preferably identical in order to simplify, and reduce cost of, manufacture. Both hub sides  24  have a stepped internal face  25  in which are formed a number of round depressions  26 , each shaped to receive, in a loose fit, a respective joint knuckle  22 . The hub sides  24  are configured such that when joined to form the assembled hub, the stepped faces  25  are aligned but separated to allow the joint knuckles  22  to be received between the hub sides  24 , and captured in the respective aligned and facing depressions  26 . The aligned and facing depressions  26 , create a plurality of spherical receiving spaces for receiving each respective joint knuckle  22 . Because the stepped faces  25  extend to the exterior of the hub, they form a slot in the hub from which frame ends  17 , secured in the joint knuckles  22 , may extend (see  FIGS. 3 ,  4 ). Preferably, the joint knuckles  22  are generally spherical in shape with the depressions having matching shape. The hub sides  24  may be cojoined via threaded fasteners or other means. 
   Preferably, each joint knuckle  22  has a pair of stub shafts  27  extending from opposite sides of the joint knuckle  22 . These are sized to be received in through-holes  28  extending through the middle of depressions  26 . Both the stub shafts  27  and through-holes  28  are aligned with the axis of rotation of the joint knuckles  22  and act to stabilize and direct the rotation of the joint knuckles—and attached frame elements. Because little force is exerted on the joint knuckle in their intended use, the stub shafts  27  need be little more that reduced-diameter half-sphere projections on the outer surface of the joint knuckles  22 . 
   In one embodiment, each joint knuckle  22  has a cylindrical cavity  30  perpendicular to its axis of rotation and passing through its center. The inside diameter of the joint cavity  30  is sized to accept a frame end  17  (not shown—see  FIG. 1 ) or other element to connect with the frame end  17 . Although the cavity  30  may be a through-hole, a blind end bore is preferred. Although in this embodiment the cavity  30  is cylindrical, other cavity geometries may be used, e.g., square or rectangular cross sections. Each joint knuckle  22  is preferably formed of molded high density plastic with integral molded stub shafts, although metals or other structural material may also be used. 
   The hub sides  24  are preferably formed of a molded high-density plastic with an open, relatively thin-walled, construction using intercostals to interconnect the hub portion containing the stepped face  25  and the other portions of the hub. In the construction shown in the figure, intercostals rigidly connect the stepped face  25  with a hub portion including a cross bar bore  32 . The axis of the cross bar bore  32  is perpendicular to the plane of the stepped face  25 , and therefore also to the plane of the retained assembled joint knuckles  22 . The cross bar bore  32  is sized to accept a cross bar  19  to form the configuration shown in  FIG. 1   b.  In final assembly and use the cross bar  19  (see  FIG. 1 ) is preferably permanently fixed in the cross bar bore  32 . Other alternative construction designs and methods are contemplated to also satisfy the functions detailed herein. 
   The depressions  26  (and retained joint knuckles  22 ) are preferably located on the stepped face  25  in an approximate circular pattern with respect to the cross bar bore centerline. In the embodiment shown, they range through an angular dimension of preferably at least 90 degrees of arc with respect to the cross bar bore  32 . The exterior, outwardly facing surface of the hub adjacent to, and bounding, the stepped face is preferably curved as shown, although this shape is not critical. 
     FIGS. 3 and 4  depict an embodiment of the inventive hub  10  including stub arms  36  connected to the joint knuckles as shown in  FIG. 2   a  (not visible in  FIGS. 3 ,  4 ). The hub  10  has a pair of exterior and outward facing bearing surfaces  34 . The bearing surfaces  34  are preferably both relatively flat and parallel to the cross bar bore centerline. The angle between the two bearing surfaces is preferably approximately 90 degrees. The junction of the two bearing surfaces  34  is preferably rounded, preferably at a radius of curvature of 1.5 inches (3.8 cm) or more. This geometry enables the hubs  10  of a canopy  100 , assembled in embodiments as shown in  FIG. 1 , to be rotated about the cross bar  19  to orient the canopy  100  in relatively opposite directions on the ground. This can be conveniently accomplished by the user, by rotating the entire canopy assembly, without lifting its entire weight, on the bearing surfaces  34  and their rounded junction. The width W 1  ( FIG. 1 ) of each hub  10 , across the bearing surfaces, should be sufficient to “float” the canopy on beach sand. A hub width W 1  of two inches (5 cm) has been found to be satisfactory. This width also provides sufficient dimension to envelope a preferred construction of the stepped face and joint knuckles. 
   In  FIGS. 3 and 4 , the joint knuckles (not visible) are joined to stub arms  36  rather than directly to canopy frame terminal ends. This structure facilitates canopy manufacture and assembly. The stub arms  36  are preferably round wood dowels, of relatively short length, which are permanently secured within respective joint knuckle cavities. They are fixed there preferably by adhesive, but alternatively by fasteners. This operation can be accomplished prior to the assembly of the joint knuckles into a hub body. This results in the hub assembly shown including the attached stub arms  36 . This assembly can then be joined with a canopy frame formed of (for example) hollow tubing by inserting the stub arms  36  into the terminal ends of the tubing. The stub arms  36  may also be considered as forming the terminal ends  17  upon assembly into a canopy. This mode of construction is simple and modular and has cost benefits which will be obvious to one skill in manufacture of products of this nature. 
     FIGS. 3 and 4  depict open and collapsed conditions, respectively, of the stub arms  36 . The open condition enables a fully opened canopy with the canopy frame opened at a quarter circle (90 degree) configuration as shown in  FIG. 1 . The collapsed condition enables the canopy to be collapsed to a reduced-space geometry for more convenient portability and storage. In the open condition, the stub arms are separated to their greatest angular extent in an open fan shape with the outermost stub arms at a respective angle of at least 90 degree. In the collapsed condition, as shown in  FIG. 4 , the stub arms  36  may be oriented in substantially mutually parallel fashion for compaction of the frame and canopy  100 . These conditions apply also in embodiments in which the joint knuckles  22  are connected directly to the canopy frame terminal ends  17 . The spacing and size of the joint knuckles and stub arms (or terminal ends) should accommodate both these conditions. 
   In a prototype device following the construction shown in the embodiments of  FIGS. 2   a,    2   b  and  3 , five stub arms  36 , having a cross-sectional diameter of ⅞ inches (2.2 cm) and a length of 12 inches (30.5 cm), are each secured in matching joint knuckles. The outside diameter of spherical joint knuckles is about 5/4 inches (3.2 cm). The five joint knuckles are spaced over 90 degrees of arc—a 22.5 degree interspacing. The radial dimension from the center bore centerline to each joint knuckle centerline of rotation is 3.9 inches (9.9 cm). The slot created by the offset stepped faces of the facing hub sides is slightly wider than the stub arm diameter. This geometry allows the stub arms to swing freely between the open (90 degree) and collapsed (mutually parallel) conditions described above. 
   The preceding embodiments and discussions are provided for example only. Other variations of the claimed inventive concepts will be obvious to those skilled in the art. Adaptation or incorporation of known alternative devices and materials, present and future is also contemplated. The intended scope of the invention is defined by the following claims.

Summary:
An improved personal shelter canopy hub is formed using a number of spherical rotating joint elements captured in a hub body. The joint elements provide rotational movement of canopy frame elements to allow easy opening and collapsing of a canopy frame and cover. An improved canopy includes two hubs joined by a cross shaft. Each hub may be formed by molding in high-density plastic and combined with stub arms to facilitate subsequent assembly of a completed canopy.