US 20020083675 A1
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.
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
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
5. An expandable assembly according to
6. An expandable assembly according to
hub elements according to
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
9. A reversibly expandable three-dimensional truss structure that is at least in part comprised of an expandable assembly according to
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
wherein the three-dimensional shape of the structure changes as it is expanded and contracted.
 This application is based on a Provisional Application, Serial No. ______, filed on Dec. 28, 2000, entitled “Connections to Make Foldable Structures.”
 The current invention relates to the construction of folding expandable truss structures for architectural use, public exhibits and folding toys.
 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.
 Utilizing the teachings of the '700 and '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 '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.
 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.
 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.
 The '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.
 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.
 The invention will be further described with reference to the accompanying drawings, wherein:
FIG. 1 is a plan view of a scissor comprised of two links.
FIG. 2 is a plan view of a scissor linkage comprised of eight scissors.
 FIGS. 3-4 are plan views of the scissor linkage in its folded and extended state respectively.
FIG. 5 is a perspective view of the scissor linkage shown with two hub elements which are basic embodiments of the invention.
FIG. 6-7 are perspective views of two scissor linkages being attached by these same hub elements.
FIG. 8 shows a third attached scissor linkage.
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.
 FIGS. 12-14 show an alternate embodiment of a hub element in perspective, plan, and elevation view.
 FIGS. 15-17 show yet another embodiment of a hub element in perspective, plan, and elevation view.
 FIGS. 18-22 show a sequence of steps for assembling a hub element to a pair of links.
 FIGS. 23-27 show another sequence of steps for assembling an alternate embodiment of a hub element to a pair of links.
 FIGS. 28-31 show an alternate embodiment of the invention that is made up of an assembly of several parts.
FIG. 32 is a plan view of a scissor linkage that is comprised of both links as well as integrated hub elements.
 FIGS. 33-34 are perspective views of two such scissor linkages being assembled together.
 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.
 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.
 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.
 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.
FIG. 3 shows scissor 1 in a folded condition. FIG. 4 shows scissor 1 in an extended condition.
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.
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.
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.
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.
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.
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.
 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.
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.
FIG. 14 shows an elevation view of element 110.
FIG. 15 shows a perspective view of element 120 which has three sections 122, 124,126.
 Section 126 is a cylindrical in form and has two grooves 128 and 129. It is centrally located within element 120.
 Section 122 extends outwards from one end of section 126 and has a pin extending from it.
 Similarly, section 124 extends from the other end of 126 and has a pin extending from it.
FIG. 16 shows a plan view of hub element 120. Central section 126 provides a pivot axis 127.
 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.
FIG. 17 shows an elevation view of element 120.
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.
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.
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.
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.
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.
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.
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.
FIG. 30 shows a plan view of hub element 150. FIG. 31 shows an elevation view of element 150.
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.
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.
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.
FIG. 36 shows a complete spherical structure 200 comprised in part of assemblies 170, 180 and 190 along with an additional nine similar assemblies.
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.
 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.