Connections to make foldable structures

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.

What is claimed is:  
     
         1 . A hub element for building expandable assemblies comprising: 
 a first connector for connecting a first scissor linkage near the center of the scissor linkage,    at least another connector located proximate to the first connector for connecting a second scissor linkage near the extremity of the second scissor linkage,    wherein each scissor linkage lies on a non-parallel plane to each other.    
     
     
         2 . A hub element according to  claim 1 , wherein the hub element can connect a pivot joint near the center of a first scissor linkage to a pivot joint located near the extremity of a second scissor linkage.  
     
     
         3 . An expandable assembly comprising: 
 at least one pair of hub elements according to claims  1  or  2 ;    at least two scissor linkages lying on non-parallel planes with each other with at least one pivot of each scissor linkage pivotally attached to the hub elements,    wherein each scissor linkage is comprised of one scissors pivotally connected to one or more adjacent scissors at the terminal pivots,    wherein each scissor has two pairs of terminal pivots and is comprised of two links pivotally connected to each other at their central pivots,    wherein each link has a central pivot and two terminal pivots, and    said scissor linkages attached to said hub elements can freely extend and retract.    
     
     
         4 . An expandable assembly according to  claim 3  that is pre-assembled.  
     
     
         5 . An expandable assembly according to  claim 3  that comes in a kit to be assembled by a user.  
     
     
         6 . An expandable assembly according to  claim 3  comprising: 
 hub elements according to  claim 1  or  2  pivotally attaching at least two scissor linkages such that the attachment points lie towards the center of one scissor linkage and towards the extremity of one or more other scissor linkages.  
 
     
     
         7 . A folding spherical linkage that is comprised in part of hub elements according to claims  1  or  2 .  
     
     
         8 . A kit of at least one expandable assembly according to  claim 3  that may be assembled to build a reversibly expandable structure.  
     
     
         9 . A reversibly expandable three-dimensional truss structure that is at least in part comprised of an expandable assembly according to  claim 3 , 
 wherein the three-dimensional shape of the structure is unchanged as it is expanded and contracted.    
     
     
         10 . A reversibly expandable three-dimensional truss structure that is at least in part comprised of an expandable assembly according to  claim 3 , 
 wherein the three-dimensional shape of the structure changes as it is expanded and contracted.