Abstract:
A new hub element is disclosed for building reversible expandable three-dimensional truss structures. The hub element can directly connect a pin joint towards the center of a scissor linkage to a pivot located near the extremity of another out-of-plane scissor linkage. It has the advantages of being more compact than previously known hub elements and can be used to create foldable structures that are more structurally sound than previously possible. The use of this novel hub element can also reduce the number of pieces required for a given foldable structure, thereby reducing manufacturing and assembly costs.

Description:
RELATED APPLICATIONS  
       [0001]    This application is based on a Provisional Application, Serial No. ______, filed on Dec. 28, 2000, entitled “Connections to Make Foldable Structures.”  
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The current invention relates to the construction of folding expandable truss structures for architectural use, public exhibits and folding toys.  
         BACKGROUND OF THE INVENTION  
         [0003]    U.S. Pat. Nos. 4,942,700 and 5,024,031, hereby incorporated by reference as if fully disclosed herein, teaches methods for constructing reversibly expandable truss-structures in a wide variety of shapes. The teachings therein have been used to build structures for diverse applications including architectural uses, public exhibits and unique folding toys.  
           [0004]    Utilizing the teachings of the &#39;700 and &#39;031 patents, self-supporting structures than maintain their overall curved geometry as they expand or collapse in a synchronized manner can be constructed. A basic building block of such structures is the “scissor” which consists of two links pinned together at mid-point, each also having pivots at their ends. These “scissors” may be further joined together in tongs-like fashion to create scissor linkages. In particular, the &#39;700 patent teaches methods for joining scissor linkages together to form these expandable structures. These methods utilize hub elements that pivotally join scissor linkages by their ends, such that the scissor linkages lie in non-parallel planes (i.e., the linkages are “out-of-plane.”) Such hub elements are small relative to the scissor links themselves, and allow adjacent scissor linkages to fold freely and synchronously.  
           [0005]    In accordance with the present invention, a new type of hub element is presented that negotiates the out-of-plane connection between scissor linkages in a novel manner. It has the advantages of being more compact than the previously disclosed hub element and can be used to create foldable structures that are more structurally sound. The use of this novel hub element can also reduce the number of pieces required for a given foldable structure, thereby reducing manufacturing and assembly costs. Further, when used for toys or novelties the hub element is less obstructive and provides a pleasing appearance, allowing the overall visual pattern of the structure to be seen clearly.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention relates to a new method of attaching scissor linkages together to make foldable structures. This method utilizes a new type of hub element that directly connects a pin joint lying towards the center of one scissor linkage to a second pivot located near the extremity of a second scissor linkage.  
           [0007]    The &#39;700 Patent taught a hub element that can only connect the end pivots of scissor linkages together. Since the center of a given scissor linkage is more stable and better supported than an endpoint, the hub element disclosed herein offers improved strength and stability. Further, a connection of this type reduces the degrees of freedom in the overall assembly and thereby enhances the level of synchronized movement between all of the links in the structure.  
           [0008]    Various embodiments of this hub element are disclosed herein. Certain elements may connect to pre-assembled scissor linkages. Other types of hub elements are integrated into a scissor linkage providing connection points that are built into the linkage. Such integrated hub elements may provide the basis for folding structures that come in kit form to be assembled by a user. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The invention will be further described with reference to the accompanying drawings, wherein:  
         [0010]    [0010]FIG. 1 is a plan view of a scissor comprised of two links.  
         [0011]    [0011]FIG. 2 is a plan view of a scissor linkage comprised of eight scissors.  
         [0012]    FIGS.  3 - 4  are plan views of the scissor linkage in its folded and extended state respectively.  
         [0013]    [0013]FIG. 5 is a perspective view of the scissor linkage shown with two hub elements which are basic embodiments of the invention.  
         [0014]    [0014]FIG. 6- 7  are perspective views of two scissor linkages being attached by these same hub elements.  
         [0015]    [0015]FIG. 8 shows a third attached scissor linkage.  
         [0016]    [0016]FIG. 9 is a perspective view of a complete spherical linkage made of six scissor linkages joined by hub elements. FIGS.  10 - 11  show the spherical linkage in its folded and extended state respectively.  
         [0017]    FIGS.  12 - 14  show an alternate embodiment of a hub element in perspective, plan, and elevation view.  
         [0018]    FIGS.  15 - 17  show yet another embodiment of a hub element in perspective, plan, and elevation view.  
         [0019]    FIGS.  18 - 22  show a sequence of steps for assembling a hub element to a pair of links.  
         [0020]    FIGS.  23 - 27  show another sequence of steps for assembling an alternate embodiment of a hub element to a pair of links.  
         [0021]    FIGS.  28 - 31  show an alternate embodiment of the invention that is made up of an assembly of several parts.  
         [0022]    [0022]FIG. 32 is a plan view of a scissor linkage that is comprised of both links as well as integrated hub elements.  
         [0023]    FIGS.  33 - 34  are perspective views of two such scissor linkages being assembled together. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    The present invention discloses a new hub element for building reversible expandable three-dimensional truss structures that can directly connect a pivot towards the center of a scissor linkage to a pivot located near the extremity of another out-of-plane scissor linkage.  
         [0025]    Referring now more particularly to the drawings, FIG. 1 shows a scissor  10  which is comprised of two links  4  and  6 . Link  4  has a center pivot  7  and two terminal pivots  2  and  5 . Link  6  is joined to link  4  by center pivot  7  and has two terminal pivots  3  and  8 . FIG. 2 shows scissor linkage  1  which is comprised of scissors  10 , 11 ,  12 , 13 , 14 , 15 , 16  and  17 . Each scissor is comprised of two links. Each link has a center pivot and two terminal pivots.  
         [0026]    Scissor  10  is situated between scissors  11  and  14 . It is attached to scissor  11  by terminal pivots  3  and  5 . It is further attached to scissor  14  by terminal pivots  2  and  8 . Thus scissor  10  shall be referred to as an attached scissor.  
         [0027]    Scissor  12  lies at the extremity of scissor linkage  1 , and is attached to scissor  13  by terminal pivots  9  and  26 . Its other terminal pivots  18  and  19  remain unattached. Thus scissor  12  shall be referred to as an unattached scissor.  
         [0028]    [0028]FIG. 3 shows scissor  1  in a folded condition. FIG. 4 shows scissor  1  in an extended condition.  
         [0029]    [0029]FIG. 5 shows a perspective view of scissor  1 . Hub elements  23  and  24  are shown in an exploded view indicating a pivot connection to be made with terminal pivot  3 . Hub elements  22  and  25  are shown in an exploded view indicating a pivot connection to be made with terminal pivot  5  In FIG. 6 hub elements  24  and  25  are shown pivotally attached to scissor linkage  1 . Scissor linkage  30  is shown in proximity to linkage  1  where terminal pivots  31  and  32  are about to be attached to hub elements  24  and  25 .  
         [0030]    [0030]FIG. 7 shows linkage  1  and linkage  30  having been joined together by hub elements  24  and  25 . Also shown are hub elements  33  and  34  which are attached to terminal pivots belonging to an attached scissor within scissor linkage  30 .  
         [0031]    [0031]FIG. 8 shows a third scissor linkage  40  which has been joined to linkage  3   0  by hub elements  33  and  34 , and has been further joined to linkage  1  by hub elements  42  and  43 . Note that hub elements serve to join terminal pivots belonging to an attached scissor pair on one linkage to the terminal pivots belonging to an unattached scissor pair on a second linkage. In simpler language, the end of each scissor linkage is joined to the middle of another scissor linkage.  
         [0032]    [0032]FIG. 9 shows a spherical linkage  100  comprised of six scissor linkages  1 , 3   0 , 40 , 50 , 60  and  70 . Hub elements join the linkages together connecting the end of each linkage to the middle of a joined linkage.  
         [0033]    [0033]FIG. 10 shows spherical linkage  100  in a folded condition. FIG. 11 shows spherical linkage  100  in an extended condition. The hub elements serve to synchronize the folding and unfolding of the six scissor linkages that comprise spherical linkage  100 .  
         [0034]    [0034]FIG. 12 shows a perspective view of hub element  110  which has three sections  112 ,  114  and  116 . Section  116  is cylindrical in form and has two grooves  117  and  118 . It is centrally located within element  110 .  
         [0035]    Section  112  extends outwards from one end of section  116  and has a hole in it. Similarly, section  114  extends from the other end of  116  and has a hole in it.  
         [0036]    [0036]FIG. 13 shows a plan view of hub element  110 . Central section  116  provides a pivot axis  117 . Terminal section  112  provides a pivot axis  113 . Terminal section  114  provides a pivot axis  115 . Terminal pivot axes  113  and  115  are non-parallel to central axis  117 .  
         [0037]    [0037]FIG. 14 shows an elevation view of element  110 .  
         [0038]    [0038]FIG. 15 shows a perspective view of element  120  which has three sections  122 ,  124 , 126 .  
         [0039]    Section  126  is a cylindrical in form and has two grooves  128  and  129 . It is centrally located within element  120 .  
         [0040]    Section  122  extends outwards from one end of section  126  and has a pin extending from it.  
         [0041]    Similarly, section  124  extends from the other end of  126  and has a pin extending from it.  
         [0042]    [0042]FIG. 16 shows a plan view of hub element  120 . Central section  126  provides a pivot axis  127 .  
         [0043]    Terminal section  122  provides a pivot axis  123 . Terminal section  124  provides a pivot axis  125 . Terminal pivot axes  123  and  125  are non-parallel to central axis  127 .  
         [0044]    [0044]FIG. 17 shows an elevation view of element  120 .  
         [0045]    [0045]FIG. 18 shows a scissor-link  130  having a hole  131  and two pins  134  and  136 . Adjoining hole  131  is a slot  133 . Hole  131  has a ridge  132 .  
         [0046]    [0046]FIG. 19 shows link  130  and hub element  120 . FIGS. 20 and 21 show element  120  being inserted through hole  131 . Pin  122  may be seen to pass through slot  133 . Groove  129  snaps into ridge  132  to retain the link and hub together.  
         [0047]    [0047]FIG. 22 shows link  130  rotated relative to element  120 . A second link  135  is shown connected to hub element  120 . Thus hub  120  provides a pivot connection to two links  130  and  135  while still offering two additional connecting points  122  and  124 .  
         [0048]    [0048]FIG. 23 shows a scissor-link  140  having a hole  141  and two holes  144  and  146 . Adjoining hole  141  is a slot  143 . Hole  141  has a ridge  142 .  
         [0049]    [0049]FIG. 24 shows link  140  and hub element  110 . FIGS. 25 and 26 show element  110  being inserted through hole  141 . Section  112  maybe seen to pass through slot  143 . Groove  118  snaps into ridge  142  to retain the link and hub together.  
         [0050]    [0050]FIG. 27 shows link  140  rotated relative to element  110 . A second link  145  is shown connected to hub element  110 . Thus hub  110  provides a pivot connection to two links  140  and  145  while still offering two additional connecting points  112  and  114 .  
         [0051]    [0051]FIG. 28 shows an alternate embodiment of a hub element. Element  150  is comprised of three separate sections  152 ,  154  and  156 . Central section  156  has two connecting blocks  157  and  158  which may be inserted into holes within sections  152  and  154 . FIG. 29 shows sections  152 ,  154  and  156  joined rigidly together.  
         [0052]    [0052]FIG. 30 shows a plan view of hub element  150 . FIG. 31 shows an elevation view of element  150 .  
         [0053]    [0053]FIG. 32 shows a scissor assembly  170  that is comprised of scissors  130 ,  135 ,  140 ,  145 ,  150  and  155 . Hub elements  110  and  120  join scissors  140  and  145  at their terminal pivots.  
         [0054]    [0054]FIG. 33 shows a scissor assembly  180  with terminal pivots  181  and  182  which are proximate to hubs  110  and  120 . FIG. 34 shows scissor assembly  180  joined to assembly  170  via hub elements  120  and  110 .  
         [0055]    [0055]FIG. 35 shows a third scissor linkage  190  which has been joined to linkage  170  by hub elements  193  and  194 . Linkage  190  has been further joined to linkage  180  by hub elements  183  and  184 . The end of each scissor linkage has been thus joined to the middle of another scissor linkage, thereby forming a triangular linkage.  
         [0056]    [0056]FIG. 36 shows a complete spherical structure  200  comprised in part of assemblies  170 ,  180  and  190  along with an additional nine similar assemblies.  
         [0057]    [0057]FIG. 37 shows spherical structure  200  in its fully folded condition. FIG. 38 shows spherical structure  100  in its fully extended condition. The hub elements serve to synchronize the folding and unfolding of the twelve scissor linkages that comprise spherical linkage  200 .  
         [0058]    It will be appreciated that the instant specification and claims set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.