You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
RELATED APPLICATIONS 
     This application claims the filing date of provisional patent application No. 60/333,418, filed Nov. 26, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     Structures that transform in size or shape have numerous applications in many fields. My prior patent, U.S. Pat. No. 5,024,031, hereby incorporated by reference as if fully disclosed herein, teaches methods for constructing expandable truss-structures in a variety of shapes. The teachings therein have been used to build structures for diverse applications including architectural uses, public exhibits and unique folding toys. 
     Such a truss structure is made up of scissor-assemblies (or “tong-assemblies”) that are connected together by hub elements. These scissor-assemblies form an open lattice-like structure that may be reversibly expanded and contracted. The structures previously disclosed are essentially expandable frameworks, no covering surfaces within the framework were provided. Such a framework can be improved upon. 
     It is, therefore, an object of this invention to provide covering surfaces within the framework of these scissor-assemblies. 
     It is a further object to provide covering surfaces for these scissor-assemblies that have a degree of structural integrity and have controlled movement when the scissor-assemblies expand and contract. 
     It is a further object of this invention to provide novel structures that, in their contracted state, have empty spaces within which the covering elements are housed. The covering elements, therefore, do not protrude outside of the contracted structure&#39;s profile. 
     It is a related object to provide novel structures that, in their extended state, the covering elements span the polygonal openings that are bordered by scissor assemblies, and are thus capable of providing an essentially complete and continuous surface. 
     The above and related objects are addressed by the instant invention. 
     SUMMARY OF THE INVENTION 
     I have invented a novel method of providing reversibly expanding covering elements for truss structures made up of scissor-assemblies that are connected together by hub elements structures. These covering elements are comprised of planar panels that are hinged together, or alternatively, comprised of a folded sheet of flexible material such as paper or a plastic sheet. 
     The benefits of such a technique are multiple. By providing a “skin” to the expandable truss structures, numerous new applications are possible. Such applications may include portable shelters, transformable lighting products, toys and games that expand with printed images, and foldable projection screens. 
     The disclosed invention thus represents a significant advance over the earlier invention, and can lead to numerous practical embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIGS. 1-4 show a covering element according to the invention. 
     FIGS. 5-7 show a covering element attached to three tong linkages. 
     FIG. 8 shows an alternate embodiment of the covering element comprised of a central six-sided polygonal element and three extensions. 
     FIGS. 9-11 show the covering element of FIG. 8 connected to three tong linkages, forming a closed-loop element with covering element. 
     FIG. 12 shows a covering element which is comprised of a ten-sided polygonal element and five extensions. 
     FIGS. 13-15 show the covering element of FIG. 12 attached to five tong linkages. 
     FIGS. 16-18 show an expanding sphere consisting of sixty tong linkages, twelve pentagonal covering elements and twenty triangular covering elements. 
     FIGS. 19-21 show an expanding dome consisting of thirty-five tong linkages, six pentagonal elements and ten triangular elements. 
     FIGS. 22-23 show an expanding sphere consisting of twenty-four tong linkages and six square covering elements. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a plan view of a covering element  50  consisting of a central hexagonal polygonal area  40 , and three extensions  42 ,  44  and  46 . In the preferred embodiment, the covering element  50  and the three extensions  42 ,  44  and  46  are constructed out of a single piece of material such as strong paper or cardboard that can withstand repeated folding and unfolding. Alternatively, plastics or other similar foldable materials may be used. Hexagonal Central area  40  is comprised of six triangular panels  1 ,  2 ,  3 ,  4 ,  5  and  6  which are formed by folds  47 ,  48  and  49  in the material of the covering element. Extension  42  is comprised of four triangular panels  10 ,  11 ,  12  and  13  and is formed by folds  47   a  and  48   a  in the material of the covering element. Likewise extensions  44  and  46  are formed by folds in the covering element and are on the same piece of material as central area  40 . 
     FIG. 2 shows covering element  50  in perspective view. FIG. 3 shows element  50  in a partially folded condition. Extensions  42 ,  44  and  46  fold inwards towards central element  40 FIG. 4 shows element  50  in a fully folded condition. It can be seen that, in the fully folded condition, the panel surfaces of the central element  40  will be hidden from view and folded inside the panels of the extensions. Also, the panels of the extensions will meet at a center point  50   a , forming an essentially continuous surface. By having different printed information/pictures on different panels, different combinations of designs can be achieved. For example, a first design can be visible when the truss structure is fully expanded, and a second design will be visible (and the first design hidden from view and folded within) when the truss structure is fully contracted. 
     FIG. 5 shows covering element  50  attached to three tong linkages  52 ,  54  and  56  by three points  57 ,  58  and  59 . These tong linkages, connected to one another to form a closed loop, can freely expand and contract. FIG. 6 shows the linkages in a partially contracted position, thereby compressing and folding up covering element  50 . FIG. 7 shows the tong linkages in their fully contracted position, which in turn fully compresses element  50 . 
     FIG. 8 shows an alternate embodiment of the invention which is a covering element  60  comprised of a central six-sided polygonal element  70 , and three extensions  71 ,  72  and  73 . Extension  71  is comprised of six triangular panels  63 ,  64 ,  65 ,  66 ,  67  and  68  formed by folds  71   a ,  72   a  and  73   a  in the material of the covering element. 
     FIG. 9 shows covering element  60  attached to three tong linkages  74 ,  75  and  76  (again forming a closed loop). The attachments of the covering element are made by hinge connections along the perimeter of the three extensions  71 ,  72  and  73 . FIGS. 10 and 11 show the tong linkages in their partially contracted and fully contracted positions respectively thereby compressing and folding up element  70 . 
     FIG. 12 shows a covering element  80  which is comprised of a ten-sided polygonal element  81  and five extensions  82 ,  83 ,  84 ,  85  and  86 . Extension  82  is comprised of eight triangular panels  87 ,  88 ,  89 ,  90 ,  91 ,  92 ,  93  and  94 . Again, the panels are formed by folds in the material of the covering element. FIG. 13 shows element  80  attached to five tong linkages  95 ,  96 ,  97 ,  98  and  99  These tong linkages are shown in their extended position. FIGS. 14 and 15 show the tong linkages in their partially contracted and fully contracted positions respectively, in turn compressing and folding up element  80 . 
     Complex structures can be created from linking together the elements (i.e., tong linkages with covering elements attached) discussed above. FIG. 16 shows an expanding sphere  100  consisting of sixty tong linkages, twelve pentagonal covering elements and twenty triangular covering elements. Expanding sphere  100  is shown in its fully compressed position. FIG. 17 shows the expanding sphere  100  in its partially folded position. FIG. 18 shows  100  in its fully extended position, the covering elements providing a “skin” for the sphere that essential covers the entire outer surface. 
     FIGS. 19,  20  and  21  show an alternate embodiment of the invention, which is an expanding dome  110  consisting of thirty-five tong linkages, six pentagonal elements and ten triangular elements. FIG. 19 shows the expanding dome  110  in its fully folded position. FIGS. 20 and 21 show  110  in its partially folded and fully extended positions respectively. 
     FIG. 22 shows another alternate embodiment of the invention which is a expanding sphere  120  consisting of twenty-four tong linkages and six square covering elements. Sphere  120  is shown in its fully compressed position. FIG. 23 shows sphere  120  in its extended position 
     In alternative embodiments of the invention, panels on the covering elements can be constructed of separate pieces of material that are attached to one another by hinges to form the covering element. 
     It will be appreciated that the instant specification, drawings and claims set forth by way of illustration and not limitation, and that various modification and changes may be made without departing from the spirit and scope of the present invention.

Summary:
Reversibly expanding covering elements for truss structures made up of scissor-assemblies that are connected together by hub elements structures. These covering elements are comprised of a folded sheet of flexible material such as cardboard or a plastic sheet, or alternatively, comprised of planar panels that are hinged together. As the truss structure expands and contracts, the covering element is compressed and expanded along with it.