Bistable pivot hinge

Abstract

Embodiments described herein take the form of a bistable hinge. The bistable hinge typically includes an elastic element and a pair of rigid structures. In the illustrated embodiments, each rigid structure includes a pair of pivoting cylinders connected to a rotating surface and a pawl formed on a portion of the rotating surface. The elastic element is held by the pawl such that a spring force of the elastic element is transmitted to the rigid structure when the elastic element is stretched. The rigid structure may contain any suitable projection, retainer, or the like around which a resilient element extends in place of the depicted pawl. As the elastic element is stretched during operation of the hinge, the elastic element maintains contact with the pawl. Further, when the hinge transitions from the closed state to the open state, the pawl stretches the elastic element, thereby applying tension thereto.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This PCT patent application claims priority to U.S. Provisional Patent Application No. 63 / 432,353, filed on December 13, 2022, entitled “BISTABLE PIVOTHINGE,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The described embodiments generally relate to a bistable hinge. More specifically, the present embodiments relate to a hinge that can be incorporated into a mechanism that transitions between an open state and a closed state, wherein the hinge is biased toward the open state or the closed state depending on the position of the hinge. Background Art

[0004] Many structures and devices utilize hinges to open or close. When balanced, a typical hinge is no more stable in any one position than in another. That is, a hinge may allow a structure to rotate, but typically does not bias the rotating structure toward an open or closed position. However, some structures or devices may be more useful or operate more efficiently when in an open or closed position. In other words, some structures containing hinges may be more useful when the structure is open or closed rather than in an intermediate position. Summary of the Invention

[0005] One embodiment described herein takes the form of a toy comprising: an expandable body; a first rotating surface attached to a first portion of the expandable body; a second rotating surface attached to a second portion of the expandable body; a first pawl attached to the first rotating surface; a second pawl attached to the second rotating surface; a bistable hinge comprising: an elastic element attached to the first rotating surface and the second rotating surface; and a pivot structure attached to the first rotating surface and the second rotating surface; wherein: the tension in the elastic element changes when the first rotating surface and the second rotating surface rotate.

[0006] The second embodiment described herein takes the form of a bistable hinge comprising: an elastic element; a first rotating surface attached to the elastic element; a second rotating surface attached to the elastic element; a first pawl attaching the first rotating surface to the elastic element; and a second pawl attaching the first rotating surface to the elastic element; wherein: when the elastic element is on a first side of a pivot plane, the elastic element biases the first rotating surface and the second rotating surface to a first position; and when the elastic element is on a second side of the pivot plane, the elastic element biases the first rotating surface and the second rotating surface to a second position.

[0007] Another embodiment described herein takes the form of a pivot structure comprising: a first pivot cylinder; a second pivot cylinder adjacent to the first pivot cylinder; a first stabilizing bar passing between the first pivot cylinder and the second pivot cylinder and attached to the first pivot cylinder; and a second stabilizing bar passing between the first pivot cylinder and the second pivot cylinder and attached to the second pivot cylinder; wherein: the first pivot cylinder and the second pivot cylinder rotate about a pivot axis defined along the adjacent surfaces of the first pivot cylinder and the second pivot cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present disclosure will be readily understood by the following detailed description with reference to the accompanying drawings, in which like reference numerals designate like structural elements, and in which:

[0009] Figure 1 The structure utilizing a bistable hinge is shown in a closed position.

[0010] Figure 2 Shown in partially open position Figure 1 , which shows the bistable hinge at maximum expansion.

[0011] Figure 3 is in a partially open position Figure 1 and Figure 2 Second view of the structure.

[0012] Figure 4 is in a partially open position Figures 1 to 3 Top view of the structure.

[0013] Figure 5 is in the fully open position Figures 1 to 4 A top view of the structure showing that the rotating surfaces contact each other when the bistable hinge is fully open.

[0014] Figure 6 is an exploded view of another example bistable hinge. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to the representative embodiments shown in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to a preferred embodiment. On the contrary, it is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the described embodiments as defined by the appended claims.

[0016] The embodiments described herein generally take the form of hinges or hinged articles that exhibit bi-stability. That is, the hinge is in equilibrium when it is open or closed and when it returns to the open or closed state in the absence of external forces. As used herein, the terms "open" and "closed" refer to two different positions of the hinge and do not necessarily require that the hinge be fully open or fully closed.

[0017] A bistable hinge typically comprises a resilient element and a pair of rigid structures. In the illustrated embodiment, each rigid structure comprises a pair of pivoting cylinders connected to a rotating surface and a pawl formed on a portion of the rotating surface. The resilient element is attached to or retained by the pawl so that the spring force of the resilient element is transferred to the rigid structure when the resilient element is stretched. The rigid structure may comprise any suitable protrusion, retainer, or the like around which the resilient element extends in place of the pawl shown. As the resilient element is stretched during operation of the hinge, the resilient element maintains contact with the pawl. Furthermore, when the hinge transitions from a closed state to an open state (or, in some cases, a partially open state), the pawl stretches the resilient element, thereby applying tension thereto.

[0018] When the bistable hinge is in its fully extended position, the elastic element is stretched to its maximum operating range (e.g., it is stretched further than at any other point during the hinge's movement and / or operation), but has not reached its elastic limit. When so stretched, the elastic element's internal spring force, resulting from placing the elastic element under tension, attempts to contract the elastic element. In the absence of any counteracting force, the elastic element will contract, returning to its resting state. This contraction of the elastic element transmits a force (the "operating force") through the retainer to the rigid structure, causing the rigid structure to pivot about its pivot axis and thereby open or close. As the rigid structure reaches its open or open state, the internal tension in the elastic element decreases, similarly reducing the rigid structure's operating force. Pivoting of the rigid structure can be stopped by parts of the rigid structure contacting one another or by features attached to the rigid structure contacting themselves or another structure (e.g., a stop).

[0019] Figure 1 An example embodiment of a bistable hinge (or simply "hinge") is shown, here incorporated into an expandable toy nose 100. Figure 1 The toy nose shown in FIG includes a hinge defined by two pairs of opposing pivot cylinders (105a and 105b, and 105c and 105d) and associated rotating surfaces 110a, 110b, and an expandable body 120 extending between the rotating surfaces. Generally, as the pivot cylinders 105a to 105d rotate, the rotating surfaces 110a to 110b move from Figure 1 Move to the closed position shown in Figures 2 to 4 The partially opened position is shown in FIG, and the final movement is to Figure 5 Thus, the "open position" of the toy nose structure 100 is a position in which the expandable body 120 is fully expanded and the rotating surfaces 110a-110b are in contact with each other. The securing strips 140a, 140b, 140c, 140d attach the rotating surfaces 110a, 110b to each other and allow rotation but not lateral movement, as discussed herein. It should be noted that Figure 1 The embodiment shown in utilizes four stabilizing bars, two for each pair of pivot cylinders. More or fewer stabilizing bars 140a-140d may be used in different embodiments. Each stabilizing bar surrounds an aperture in which a detent 135 is positioned, as will be described below. In addition, each stabilizing bar 140a-140d surrounds an aperture on a first side of the first rotating surface 110a and a second aperture on an opposite side of the second rotating surface 110b. Figure 6 Describe the stabilization bar, its function and operation in more detail; Figure 1 The stability bar is like Figure 6 The same functions as those of the stabilizing bars.

[0020] like Figures 1 to 5 As shown in FIG, the bistable hinge transitions between various states as the toy nose moves from its closed position to its open position. As the hinge opens and closes, the hinge moves rotationally, but not laterally. Furthermore, the hinge rotates about a pivot axis 125 defined along a line that intersects the contact surfaces of the pivot cylinders 105a-105d (e.g., the points at which opposing pivot cylinders 105a-105b and 105c-105d contact one another). Figure 1 showing the bistable hinge and toy nose in the closed state, Figure 2 showing the bistable hinge and toy nose in a partially open state, Figure 3 is another view of the bistable hinge and toy nose in a partially open position, Figure 4is another view of the bistable hinge and toy nose in a partially open state, and Figure 5 The bistable hinge and toy nose are shown in an open state.

[0021] Usually, such as Figure 1 As shown in FIG, one or more elastic elements 130a to 130b are wound around the pawl 135 of each rotating surface. Figures 1 to 5 In the embodiment shown in FIG, there are two elastic elements 130a-130b and four detents 135a-135d, but some embodiments may use more or fewer elastic elements and / or detents. In some embodiments, detent 135 may be replaced by a groove, depression, or the like, rather than being formed as a protrusion. Rotational surface 110a rotates in a first direction, such that expandable body 120 is clamped between semicircular rotational surfaces 110a, 110b. The elastic element 130 is sized so that it is under tension when the hinge is closed.

[0022] Typically, as the rotating surfaces 110a, 110b open or close, the rotating surfaces 110a, 110b pivot about a pivot axis. In operation, the hinge has a first side and a second side (e.g., a combination of the rotating surface 110 and one or more fixed pivot cylinders 105) that move away from or toward each other depending on how open or closed the hinge is at any given moment. For example, when the toy nose 100 is moved from Figure 1 The closed state transitions to Figure 2 During the partially opened state, the first side and the second side of the hinge are closed as shown by Figure 1 The first and second sides of the hinge move away from each other. Similarly, when the toy nose 100 is moved from Figures 2 to 4 The partially open state transitions to Figure 5 In the closed state, the first side and the second side of the hinge are in Figures 2 to 4 In the partially opened state shown in FIG, the hinge is in the maximum extended state, with the first and second sides of the hinge pivoting towards each other. The movement of these sides is always a rotation around the pivot axis 125.

[0023] As the hinge opens and the rotating surfaces 110a, 110b rotate away from each other, the tension in the elastic element 130 increases. Figures 2 to 4When in the partially open position shown in FIG, the hinge is in its most expanded state. That is, the most expanded state occurs when the sides of the bistable hinge are in the same plane with each other. Typically, although not necessarily, this also places the pivot axis 125 in the same plane as the hinge's rotational surfaces 110a, 110b. Then, when the toy nose 110 is moved from Figures 2 to 4 The partially opened position is converted to Figure 5 to the fully open position, or when Figures 2 to 4 The partially open position is converted to the attached Figure 1 When the hinge is in the closed position, the hinge contracts (e.g., the rotating surfaces 110a, 110b move toward each other). In other words, the hinge contracts whenever the rotating surfaces 110a, 110b of the hinge move toward each other, and expands whenever the rotating surfaces 110a, 110b of the hinge move away from each other.

[0024] The expansion of the bistable hinge increases the tension in the elastic element 130, while the contraction of the hinge reduces the tension in the elastic element. As the hinge expands, the pawl 135 defined on the first rotating surface 110a moves away from the pawl defined on the second rotating surface 110b, which stretches the elastic element 130 and increases its internal tension. When the hinge contracts, the pawl 135 on the first rotating surface moves toward the pawl on the second rotating surface, which relaxes the elastic element 130 and reduces its internal tension.

[0025] In the absence of any external forces, the elastic element 130 always seeks to reduce tension. Thus, if free of such external forces, the elastic element will always pull the hinge's rotating surfaces 110a, 110b toward each other (e.g., causing them and the associated pivot cylinder 105 to rotate about the pivot axis 125), unless the rotating surfaces are in an unstable equilibrium state with perfectly balanced tension about the pivot axis, which is typically short-lived and extremely difficult to achieve at best. Thus, the system's steady state typically occurs only when the hinge is fully open or fully closed and the elastic element 130 seeks to return the hinge to that state.

[0026] In effect, the internal tension of the resilient element 130 attempts to move the resilient element from an extended state to a relaxed or contracted state (except when the resilient element is in such a contracted or relaxed state). As the resilient element 130 wraps around the various detents 135 and, in this embodiment, around the sides of the hinge, the effect of this pulling within the resilient element is to pull the hinge's rotating surfaces 110a, 110b toward each other, e.g., causing the hinge to rotate about its pivot axis 125, thereby moving these surfaces closer together.

[0027] At any given moment, a substantial portion of the elastic element 130 lies on one side or the other of a plane (the "pivot plane") containing the instantaneous axis of rotation (the "pivot axis" 125). Typically, the pivot plane is coplanar with the force vector generated by the tension in the elastic element 130. Often, but not necessarily, the pivot plane is coplanar with the surfaces of rotation 110a, 110b when the bistable hinge is maximally extended.

[0028] As the elastic element 130 seeks to contract, the elastic element 130 will attempt to contract in such a way that the elastic element 130 pulls the hinge's rotational surfaces 110a, 110b toward each other on the side of the pivot plane where the majority of the elastic element lies. Thus, if the majority of the elastic element is on a first side of the pivot plane, the elastic element 130 will pull the hinge to its open position (e.g., Figure 1 If the majority of the resilient element is on the second side of the pivot plane, the resilient element 130 will pull the hinge to its closed position (as shown). Figure 5 (As shown). This also pulls the rotating surface together with the pull hinge by forcing the paired pivot cylinders 105a-105b, 105c-105d to rotate about the pivot axis 125, thereby opening or closing the toy nose and expanding or contracting the expandable body. The pivot cylinders 105a, 105c contact their opposing pivot cylinders 105b, 105d at the pivot axis 125, but the point on each pivot cylinder's surface where it contacts its opposing cylinder's surface varies as the pivot cylinders rotate.

[0029] Thus, the hinge has three equilibrium points, two of which (corresponding to the hinge being fully closed or fully open) are stable, and one of which (corresponding to the hinge being in Figure 2 The partially opened state shown in FIG, in which the two rotating surfaces 110 a, 110 b are coplanar) is unstable.

[0030] As the pivot cylinders 105a to 105d rotate, the rotating surfaces 110a to 110b move and the associated bistable hinges open or close, a substantial portion of the resilient element 130 passes through the pivot plane as the pawl 135 passes through the pivot plane. Figure 1 The elastic element 130 shown in FIG. Figure 5 The elastic element shown in is compared. Figure 1 In the embodiment, the entire elastic element 130 is located on the first side of the pivot plane, while Figure 5 The entirety of the elastic element is located on the opposite second side of the pivot plane. Thus, when the toy nose and the hinge are in Figure 1 , the spring element holds the toy nose closed. Similarly, when the toy nose and hinge are in Figure 5When in the configuration shown in , the elastic element holds the toy nose open.

[0031] Combine this with Figure 2 In contrast, Figure 2 The majority of the elastic element is located on a first side of the pivot plane, while a smaller portion of the elastic element is located on a second side of the pivot plane. Figure 2 When no force is applied to the hinge or toy nose in the configuration shown in FIG, the elastic element will contract and return the toy nose to Figure 1 In contrast, if the pivot cylinders 105a to 105d continue to rotate (eg, the rotating surfaces 110a to 110b continue to rotate about the pivot plane 125), as when the toy nose 100 is rotated from Figure 2 The configuration is converted to Figure 5 As happens when the toy nose is in the right configuration, the majority of the elastic element passes through the pivot plane to the opposite side. At this point, the elastic element will bias the hinge open and thus pull the toy nose toward Figure 5 open position.

[0032] Since the hinge stops moving only when it is fully open or fully closed (e.g., retracted), the hinge is bistable. The hinge has two substantially equal resting states, fully open and fully closed, to which it always seeks to return.

[0033] In addition to utilizing a spring element to provide bistability, the toy nose incorporates a unique pivot structure into the bistable hinge. Generally, in embodiments, the pivot structure can be used as part of a hinge with or without a spring element, and vice versa. It is not required that both the spring element and the pivot structure be incorporated into a single hinge, and they often are not.

[0034] Figure 6 Suitable for incorporation Figures 1 to 5 Exploded view of the pivot structure 600 in the bistable hinge of the toy nose shown in . The operation of the pivot structure 600 is similar to that of the embodiments shown with reference to those figures, although the pivot structure 600 differs in certain respects, for example by using differently shaped stabilizing bars. The pivot structure 600 includes a plurality of pivot cylinders 610a, 610b, 610c, 610d that are held in position against one another and are configured to rotate about a pivot axis while maintaining contact between opposing pivot cylinders. The pivot cylinders may be held against one another by first and second stabilizing bars 615a, 615b that also attach the first and second rotating surfaces 605a, 605b to one another. The pivot cylinders may be attached to the rotating surfaces or may be formed integrally with the rotating surfaces. In Figure 5 In the embodiment shown in the exploded view of FIG, each rotating surface is fixed to or formed with a pair of pivot cylinders. For example, the first rotating surface 605a is fixed to or formed with the first pivot cylinder 610a and the third pivot cylinder 610c, while the second rotating surface 605b is fixed to or formed with the second pivot cylinder 610b and the fourth pivot cylinder 610d. Some embodiments may include a rotating surface 605 that is fixed to or formed with a single pivot cylinder 610, while other embodiments may use three or more pivot cylinders for each rotating surface. The pivot cylinder 610 may extend along the entire edge or side of the rotating surface 605, or may extend along only a portion of the rotating surface.

[0035] The stabilizing bar 615a is attached to a first side of the first rotating surface 605a and its associated pivot cylinders 610a, 610d. The stabilizing bar 615a passes between the first pivot cylinder 610a and the second pivot cylinder 610b, and likewise between the third pivot cylinder 610c and the fourth pivot cylinder 610d, and is attached to the opposite side of the second rotating surface 605b. That is, if the stabilizing bar 615a is attached to the "top" surface of the first rotating surface 605a (refer to FIG. 1 ), the stabilizing bar 615a will not rotate. Figure 5 ), a stabilizing bar 615b is similarly attached to the "bottom" surface of the second rotating surface 605b. Similarly, a second stabilizing bar 615b is attached to the opposite side of the first rotating surface 605a and the first side of the second rotating surface 605b, again passing between each pair of adjacent / adjacent pivot cylinders (e.g., pivot cylinders 610a and 610b, and pivot cylinders 610c and 610d).

[0036] The stabilization bar generally holds the first and second rotating surfaces in position relative to one another, allowing rotational movement of the rotating surfaces toward or away from one another about a pivot axis, but preventing non-rotational movement relative to one another. Because the stabilization bars are not elastic, they resist any linear force (e.g., a force that places the stabilization bar under tension) that attempts to move the rotating surfaces laterally or out of plane away from one another. However, because the stabilization bar is flexible, it permits rotational movement of the rotating surfaces about a pivot axis defined at the abutment of the respective pivot cylinders of these surfaces. The stabilization bar similarly holds the opposing pivot cylinders in their abutted position while simultaneously permitting rotation of the opposing pivot cylinders about the pivot axis.

[0037] Furthermore, and as mentioned above, each stabilization bar is secured to a first side of one rotating surface and an opposite side of the other rotating surface, passing between the pivot cylinders and thus through the pivot axis, thereby securing the rotating surfaces to each other. Thus, when the rotating surfaces pivot toward or away from each other, one side of the stabilization bar is placed in tension, while the other side is in compression. Furthermore, the tension / compression profile of one stabilization bar is opposite that of the other, to the extent that they are attached to opposite sides of the rotating surfaces. This promotes uniform and smooth movement when pivoting the rotating surfaces toward or away from each other (e.g., when opening or closing a toy nose).

[0038] Each stabilization strip can include a pair of cutouts or recesses 620a-620d defined in a portion of the strip that passes between the pivot cylinders 610a-610d. With respect to the first stabilization strip 615a, the cutouts 620a, 620b are located along the outer edge of the strip, while the cutouts 620c, 620d of the second stabilization strip 615b are located along the inner edge of the strip. Generally, the cutouts 620a, 620b are sized so that each stabilization strip 615a, 615b can pass between a pair of pivot cylinders (e.g., cylinders 610a and 610b, and cylinders 610c and 610d) without the strips overlapping. To this end, stabilization strip 615a passes between the pair of pivot cylinders along the inner edge, while the other stabilization strip 615b passes between the pair of pivot cylinders along the outer edge of the cylinders. Although a pivot cylinder may be described herein as abutting another pivot cylinder, it should be understood that such description encompasses embodiments in which a pivot cylinder abuts a stabilizing bar attached to or adjacent to an opposing pivot cylinder.

[0039] Stabilizing bars 615a, 615b hold the pairs of pivoting cylinders 610a, 610b and 610c, 610d aligned with each other and generally prevent lateral movement of the cylinders while allowing rotational movement. Each pivoting cylinder 610a to 610d is clamped between stabilizing bars 615a, 615b extending around them, as are the associated rotating surfaces 605a, 605b. Thus, stabilizing bars 615a, 615b allow the rotating surfaces 605a, 605b to rotate toward or away from each other while prohibiting or restricting lateral movement away from each other. Figure 1 and Figure 2 Stabilizing bars 615a, 615b are shown extending around the first pair of pivot cylinders 610a, 610b and the second pair of pivot cylinders 610c, 610d.

[0040] The pawls 625a to 625d extend from the narrow portion of the rotating surfaces 605a, 605b. The ends of the elastic element are typically wrapped around the opposing first and second pawls 625a, 625b, while the body of the elastic element passes through the opposing third and fourth pawls 625c, 625d and is fixed in place and tensioned by them. As the rotating surfaces 605a, 605b move toward each other, the elastic element relaxes (e.g., its internal tension decreases), and as they move away from each other, the elastic element stretches (e.g., its internal tension increases). The overall effect of tension on the elastic element is discussed above. Figure 5 As shown in , some embodiments may use two detents for each end of the elastic element, while other embodiments may wrap the ends of the elastic element around a single detent, such as Figure 1 As shown in .

[0041] When the hinge is opened (e.g., when the hinge Figure 1 The position shown in the Figure 2 ), as the pivot cylinders 610a-610d rotate about the pivot axis 1XX, the rotating surfaces 605a, 605b rotate away from each other. Stabilizing bars 615a, 615b constrain the movement of the rotating surfaces and the pivot cylinders, forcing them to rotate about the pivot axis. Similarly, and as previously discussed, the stabilizing bars generally prevent or inhibit lateral movement of the rotating surfaces relative to each other.

[0042] The rotation of the hinge about the pivot axis means that each of the pivot cylinders 610a to 610d "rolls" around the surface of the opposing pivot cylinder; each of the pivot cylinders in the pair rotates the same distance. As this happens, the elastic element stretches, to the extent that the elastic element wraps around one or more detents that move away from each other when the hinge initially opens (e.g., the hinge structure moves away from the hinge). Figure 1 The configuration is converted to Figure 2 Typically, the elastic element seeks a position where its internal tension is reduced. In other words, once stretched, the elastic element seeks to contract. Figure 1 The configuration is converted to Figure 2 When initially opened during the configuration of Figure 1 The hinge is biased toward a closed configuration. In other words, the resilient element exerts a force on the rotating surfaces (via the associated detents) that resists opening and seeks to move the rotating surfaces toward each other back to the hinged structure's closed position. If the user releases one of the rotating structures, it will rotate about the pivot axis toward the other rotating structure, moving in the opposite direction of the rotational motion experienced when the hinged structure was opened.

[0043] Once the rotating surface of the articulated structure moves past Figure 2 , as shown in the position (e.g., once the pivoting cylinder and the rotation of the rotating surface drive the rotating surface through Figure 2 position), in the absence of external force, the elastic element will cause the hinge structure to switch to Figure 5 The spring element will always bias the rotating surfaces to rotate the shortest distance necessary for them to contact each other, or as close to each other as possible if stops or offsets prevent contact. Pairs of pivoting cylinders facilitate the rotational motion of the rotating surfaces, while the stabilizing bars align and maintain the rotating surfaces relative to each other.

[0044] As the hinged structure Figure 1 Movement from the fully closed position to Figure 5 In the fully open position, the honeycomb material expands to form a sphere or a portion of a sphere. The size, pattern, and density of the honeycomb material may vary between embodiments.

[0045] While hinged structures have been generally discussed in the context of toys (such as toy noses), it should be understood that hinged structures can be used in many different devices, objects, and contexts. For example, a hinged structure can form the spine (or a portion of the spine) of a book. A hinged structure can be used as a door hinge, as part of a wallet, incorporated into a fan, and so on. A device or object can use a single hinged structure or multiple hinged structures to facilitate the pivoting opening and closing of the device or object. In certain embodiments, the pivoting surface can be replaced by a flexible member or other structure. In some embodiments, the pivoting surface may not be semicircular as shown, but instead may be a parallelepiped, triangular, or other polyhedral shape, or an irregular shape. Embodiments may utilize a pivoting cylindrical structure without an elastic element, or utilize an elastic element without a pivoting cylindrical structure (for example, where the pivoting cylinder is replaced by a flexible or living hinge). Other variations beyond those listed herein are also possible.

[0046] For purposes of explanation, the foregoing description uses specific terminology to provide a thorough understanding of the described embodiments. However, those skilled in the art will appreciate that specific details are not required to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Those skilled in the art will appreciate that numerous modifications and variations are possible in light of the foregoing teachings.

Claims

1. A toy, comprising: Expandable body; a first surface of rotation attached to a first portion of the expandable body; a second surface of rotation attached to a second portion of the expandable body; a first pawl attached to the first rotating surface; a second pawl attached to the second rotating surface; A bistable hinge, comprising: an elastic element attached to the first rotating surface and the second rotating surface; and a pivot structure attached to the first rotating surface and the second rotating surface; wherein: As the first rotating surface and the second rotating surface rotate, the tension in the elastic element changes. 2 . The toy according to claim 1 , further comprising a stabilizing bar securing the first rotating surface to the second rotating surface.

3. The toy according to claim 2, wherein: The stabilization bar is a first stabilization bar; and A second securing bar further secures the first rotating surface to the second rotating surface.

4. The toy according to claim 2, wherein: The securing bar is secured to a first surface of the first surface of rotation and to an opposing second surface of the second surface of rotation.

5. The toy according to claim 1, wherein: As the first rotating surface and the second rotating surface move away from each other, the tension in the elastic element increases; and As the first rotating surface and the second rotating surface move toward each other, tension in the elastic element decreases.

6. The toy according to claim 1, wherein: said expandable body defining a honeycomb shape; and As the first rotating surface and the second rotating surface move away from each other, the expandable body expands.

7. A bistable hinge, comprising: elastic element; a first surface of rotation attached to the elastic element; a second surface of rotation attached to the elastic element; a first pawl attaching the first rotating surface to the elastic element; as well as a second pawl attaching the first rotating surface to the elastic element; wherein: When the elastic element is located on a first side of a pivot plane, the elastic element biases the first rotating surface and the second rotating surface to a first position; and When the elastic element is located on a second side of the pivot plane, the elastic element biases the first and second rotating surfaces to a second position.

8. The bistable hinge according to claim 7, wherein: The pivot plane includes a pivot axis about which the first and second surfaces of rotation rotate.

9. The bistable hinge according to claim 7, wherein: As the bistable hinge opens, the internal tension of the elastic element increases; and As the bistable hinge closes, the internal tension in the elastic element decreases.

10. The bistable hinge according to claim 7, wherein: The first and second surfaces of rotation rotate about a pivot axis within the pivot plane; and The first rotating surface and the second rotating surface are constrained from moving laterally relative to each other.

11. The bistable hinge according to claim 10, further comprising at least one stabilizing bar fixed to the first rotating surface and the second rotating surface, wherein The at least one fastening strip allows the first and second rotating surfaces to rotate, but constrains the first and second rotating surfaces from moving laterally relative to each other.

12. The bistable hinge according to claim 7, wherein: When the first rotating element and the second rotating element are in the pivot plane or parallel to the pivot plane, the elastic element is in an unstable equilibrium state relative to the pivot axis.

13. A pivot structure, comprising: a first pivoting cylinder; a second pivoting cylinder adjacent to the first pivoting cylinder; a first stabilizing bar passing between the first pivot cylinder and the second pivot cylinder and attached to the first pivot cylinder; as well as a second stabilizing bar passing between the first pivot cylinder and the second pivot cylinder and attached to the second pivot cylinder; wherein: The first pivot cylinder and the second pivot cylinder rotate about a pivot axis defined along abutment surfaces of the first pivot cylinder and the second pivot cylinder.

14. The pivot structure according to claim 13, wherein: The first stabilizing bar is also attached to the second pivot cylinder; and The second stabilizing bar is also attached to the first pivot cylinder.

15. The pivot structure according to claim 13, wherein: The first stabilizing bar and the second stabilizing bar allow the first pivot cylinder and the second pivot cylinder to rotate about the pivot axis; and The first and second stabilization bars prevent lateral movement of the first and second pivot cylinders relative to each other.

16. The pivot structure according to claim 13, further comprising: a third pivot cylinder attached to the first pivot cylinder via a first surface of rotation; as well as a fourth pivoting cylinder attached to the second pivoting cylinder via a second surface of rotation; wherein: The third pivot cylinder and the fourth pivot cylinder rotate about the pivot axis; and The pivot axis intersects abutment surfaces of the third pivot cylinder and the fourth pivot cylinder.

17. The pivot structure according to claim 16, wherein: The first stabilizing bar is also attached to the third cylinder; The second stabilizing bar is also attached to the fourth cylinder; The first stabilizing bar passes through the pivot axis; and The second stabilizing bar passes through the pivot axis.

18. The pivot structure according to claim 17, wherein: The first stabilization strip defines a first cutout; The second stabilization strip defines a second cutout; and The first and second cutouts allow the first and second stabilization strips to pass through the pivot axis without laterally overlapping each other.

19. The pivot structure according to claim 18, wherein: The stabilizing bar allows the pivot cylinder to rotate 180 degrees about the pivot axis.

20. The pivot structure according to claim 17, further comprising: a first rotating structure attached to the first pivot cylinder, the second pivot cylinder, the first stabilizing bar, and the second stabilizing bar; as well as a second rotating structure attached to the third pivot cylinder, the fourth pivot cylinder, the first stabilizing bar, and the second stabilizing bar; wherein: The first and second stabilizing bars allow the first and second rotating structures to rotate about the pivot axis but inhibit lateral movement of the first and second rotating structures relative to each other.

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