Abstract:
A frame structure having a truss comprising three longitudinal members the longitudinal alignment of which is facilitated by a stopper member that prevents a junction of the three members from pivoting beyond a desired angle.

Description:
FIELD OF THE INVENTION 
     The present invention relates to portable shelters and, more particularly, to reinforced frame structures that support portable shelters. 
     BACKGROUND OF THE INVENTION 
     The evolution of light-weight, easily erected and economical portable shelters has led to the increasing commercial and private use of these structures. Portable shelters typically employ a cloth or plastic material attached to a light-weight, highly foldable skeleton or frame structure. The cloth provides a roof and/or walls for the shelter, and the frame structure provides support for the cloth, for example, the frame structure includes legs to elevate the roof and a system of trusses to support the roof and to generally stabilize the shelter. The frame structure often incorporates a compound, scissor-like, arrangement of a light-weight, tubular material such as aluminum. In order to maximize the usable area under a shelter, the frame structure is often designed so that the roof is supported solely by legs positioned near the perimeter of the roof. Stated alternatively, shelters do not typically employ an interior supporting post or leg such as a leg or post positioned in the center of shelter. U.S. Pat. No. 4,641,676 to Lynch and U.S. Pat. No. 7,367,348 to Tsai et al., the contents of which are herein incorporated by reference, are examples of such portable shelters. 
     Unfortunately, the design objectives of internally unsupported roofs and light-weight and foldable frame structures, often results in portable shelters that are unstable in wind and that suffer from sagging or collapsing roofs and peaks. What is needed in the art is a frame structure for a portable shelter that provides increased stability and prevents sagging and collapsing while maintaining the design objectives of maximizing usable space, foldability, and light-weight. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a frame structure for portable shelters that has enhanced stability and resists sagging and collapse. A further objective of the present invention is to achieve the above objectives without sacrificing the usable space under the portable shelter and without adversely affecting the foldability and weight of the portable shelter. These objectives are achieved by employing a frame structure having a peak truss comprising three longitudinal members the longitudinal alignment of which is facilitated by a stopper member that prevents a junction of the three members from pivoting beyond a desired angle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a frame structure for a portable shelter according to one embodiment of the present invention. 
         FIG. 1B  is a perspective view of a frame structure for a portable shelter according to one embodiment of the present invention. 
         FIG. 2  is a perspective view of a portion of a frame structure according to one embodiment of the present invention. 
         FIG. 3  is a magnified, perspective view of the truss junction  30  shown in  FIG. 2 . 
         FIG. 4  is a magnified, bottom view of the truss junction  30  shown in  FIG. 2 . 
         FIG. 5  is a magnified, perspective view of the truss junction  30  shown in  FIG. 2 . 
         FIG. 6  is a perspective view of a portion of a frame structure according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
     The frame structure for the present portable shelter provides increased stability and prevents sagging and collapsing of the shelter while maintaining the design objectives of maximizing usable space, foldability, and light-weight. 
       FIGS. 1A and 1B  show a reinforced frame structure according to one embodiment of the present invention, and  FIGS. 2 and 6  show partial views of reinforced frame structures according to certain embodiments of the present invention. As shown, frame  10  employs legs  12  which extend upward from the ground to a corner junction  14 . The corner junction  14  attaches primary side trusses  16  and peak trusses  18  to the leg  12 . Secondary side trusses  20  are attached at one end to the leg  12  at a point between the end of the leg  12  resting upon the ground and the corner junction  14  and are attached at an intermediary point  22  along a length of the primary side truss  16 . Each of the peak trusses  18  are attached to one another at a peak junction  24 . A truss support  26  may also be employed to extend from the peak truss  18  to the leg  12  at a point between the end of the leg  12  resting upon the ground and the corner junction  14  so as to vertically support the peak truss  18 . 
     When a portable shelter according to the present invention is in an open, expanded state, the peak junction  24  will be positioned in a location in the approximate center of the horizontal area occupied by the shelter and elevated above the height of the top of the legs  12 . In this manner, the peak junction  24  forms a peak or high-point of the roof of the frame  10 . 
     Of particular importance to achieving the objectives of providing a frame structure having increased stability while also preventing sagging and collapsing of the shelter roof is the configuration of the peak trusses  18 . As shown in  FIG. 2 , a first end of a single truss  32  is attached to the peak junction  24 . A second end of the single truss  32  is interposed between the members of a truss pair  34  and attached to the truss pair by fastener  38 , shown in  FIGS. 3-5 . The opposite end of the truss pair  34  is attached to the corner junction  14 . 
       FIGS. 3 and 4  show the configuration of the truss junction  30  when the frame structure  10  is in a fully expanded or open state. Note that the single truss  32  and the truss pair  34  are oriented longitudinally along a common axis when in the open state.  FIG. 5  shows the configuration of the truss junction  30  when the frame structure is in an intermediate or closed state. In a non-open state, the single truss  32  and the truss pair  34  are not oriented longitudinally along a common axis. As shown best in  FIG. 5 , a stopper fastener  40  attaches a stopper  36  to the single truss  32 . When transforming the frame structure  10  from the closed to the open, expanded state, the stopper  36  provides a surface  42  against which the truss pair  34  will contact and prevent further rotation once the frame structure  10  has been expanded to the open state. Accordingly, the stopper  36  assists in longitudinally aligning the single truss  32  and the members of the truss pair  34  when the frame structure is in the open state. Once aligned, the peak truss  18  provides a three member truss junction  30 , the single truss  32  interposed between the two members of the truss pair  34 , that has enhanced lateral rigidity to resist wind and other lateral forces. The three member truss junction  30  also provides enhanced rigidity against sagging and collapsing due to vertical loads such as rain. 
     While the stopper  36  has been described as being attached to the single truss  32 , it will be understood by those of ordinary skill in the art that the stopper may also be attached to the truss pair  34  in order to achieve the same objectives. For example, as shown in  FIG. 5 , the fastener  38  attaches the approximate ends of the truss pair  34  to the single truss  32  at a point proximal to the end of the single truss  32 . This design allows for a significant overlap between the single truss  32  and the truss pair  34 , thereby providing a three member truss junction  30 . In an alternative embodiment, the fastener  38  attaches the approximate ends of the single truss  32  to the truss pair  34  at a point proximal to the end of the truss pair  34 . In this embodiment, the stopper  36  is attached to the approximate ends of the truss pair  34 . 
     One of skill in the art will also recognize that the frame structure  10  of the present invention may be constructed from a variety of materials known in the art to facilitate light-weight designs and foldability, including tubular or solid aluminum. For example,  FIG. 6  shows an embodiment of the present invention differing from that shown in  FIGS. 2 through 5  in that the truss  32  and the truss pair  34  employ a narrower shape fabricated from a solid material. In order to provide the desired spacing between the truss pair  34  and the single truss  32 , spacers  44  are employed between the trusses such that the fastener  38  passes through the single truss  32 , the truss pair  34 , and two spacers  44 . One spacer  44  being interposed on each side of the single truss  32 . The embodiment provides for easier, more compact folding of the frame structure  10  due to the reduced cross-sectional shape of the truss members. 
     The fastener  38  and the stopper fastener  40  may employ a bolt, screw, pin, or other suitable means for attachment known in the art. 
     Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.