Extensible structure

Abstract

Extensible structure (15a, 15b) comprising a plurality of support frames (40a, 40b, 45a, 45b, 50a, 50b, 55a, 55b, 60a, 60b, 65b), of which at least a first support frame (40a, 40b) rigid and a second rigid support frame (45a, 45b), each equipped with a first face (70a, 70b) and an opposite second face (75a, 75b). Said extensible structure also comprising a plurality of bistable cells (100) interposed between the first support frame and the second support frame, comprising at least a first cell (100) and a second cell (100), each equipped with a first section of connection (105) and a second connection section (110), which connection sections are movable with respect to each other along an extension direction (A) of the cell itself, transversal to the first face (70a, 70b) and to the second face (75a, 75b) of the first support frame (40a, 40b) and of the second support frame (75a, 75b), said bistable cells (100) each being movable between a first stable position, wherein the connection (105, 110) are at a minimum mutual distance along the extension direction (A), and a second stable position, wherein the connecting sections (105, 110) are at a maximum mutual distance along the extension direction (A), wherein the first connection section (105) and the second connection section (110) are configured to connect the respective cell (100) to the first connection section (105) of another cell and second connection section (110) of another cell and to the first or second support frame. Said first and second cells (100) connect the first and second support frames independently to each other, and the variation of the position between the first stable position and the second stable position of said cells causes a variation, along the said direction of extension (A), of a mutual distance of the first support frame (40a, 40b) from the second support frame (45a, 45b).

Description

[0001] EXTENSIBLE STRUCTURE

[0002] * * *

[0003] TECHNICAL FIELD

[0004] The present invention concerns an extensible structure, habitable or not, intended to be installed preferably in an extraterrestrial environment, suitable for creating outposts for scientific, technical, mining, military, tourist and colonization activities, ortransportable shelters or service modules, also for emergency situations, including, in certain circumstances, also ground operations.

[0005] By "extraterrestrial environment" we mean, here, the orbital space of a generic celestial body, including the Earth, the surface of a generic celestial body, excluding the Earth, or interplanetary space.

[0006] KNOWN TECHNIQUE

[0007] From document WO2018189719 of the same Applicants, extensible energy storage structures consisting of a network of bistable cells are known. These bistable cells are each equipped with a first portion and a second portion, which are movable with respect to each other along a direction of extension of the cell itself, and a third and fourth portion which are movable with respect to each other along a direction perpendicularto the direction of extension. The cells, as mentioned above, constitute a network, in which at least two of the said portions are in common with the adjacent cells. In particular, the first and fourth portions are in common with a second adjacent cell, the fourth and second portions are in common with a third adjacent cell, the second and third portions are in common with a fourth adjacent cell and the first and the third portion are shared with a fifth adjacent cell.

[0008] Each cell is operable between a first stable position, in which the first and second portions are at a minimum distance from each other along the extension direction, while the third and fourth portions are at a maximum distance from each other, and a second stable position, wherein the first and second portions are at a maximum mutual distance along the extension direction, while the third and fourth portions are at a minimum mutual distance.

[0009] By compressing or extending said web, bringing the cells into the first or second stable position, it is possible to modify the extension of the structure.

[0010] This construction is characterized by non-linear resilientity, is extremely versatile and is in fact used for the dampening of stresses, such as deriving from shocks or impacts. A problem with this solution is that as it extends and retracts, the width transverse to its extension direction varies and the lattice must be created ad hoc for each application.

[0011] A more traditional extensible structure is known from document US5086999, which describes telescopic structures for aerospace use formed by hollow modules slidingly associated with each other. A problem with this solution is that by relying on telescopic elements, the use of space is not optimal, since due to construction needs the cross section of the structure is not constant. Furthermore, the telescopic structures of document US5086999 are not designed to be dismantled and reconfigured.

[0012] SUMMARY OF THE INVENTION

[0013] The aim of the present invention is to improve the solutions of extensible structures proposed by the prior art, in particular by making available a robust and efficient extensible structure, whose cross-section, measured transversely to an extension direction, is substantially constant.

[0014] In particular, the invention makes available an extensible structure comprising: a plurality of support frames, of which at least a first support frame, which is rigid, and a second support frame rigid, which is rigid, each equipped with a first face and an opposite second face, - a plurality of bistable cells interposed between the first support frame and the second support frame, comprising at least a first cell and a second cell, each equipped with:

[0015] • a first connection section and a second connection section, which connection sections are movable with respect to each other along an extension direction (A) of the cell itself, transversal to the first face and to the second face of the first support frame and of the second support frame,

[0016] • a first beam and a second beam, rigid, each equipped with a first longitudinal end and a second longitudinal end, wherein the respective first longitudinal ends are hinged to each other at the first connection section and the second longitudinal ends are rotatable with respect to the second connection section, and

[0017] • a resilient element which generates a force in the direction of mutual approach of the second longitudinal ends of said beams, said bistable cells each being movable between a first stable position, in which the connecting sections are located at a minimum mutual distance along the extension direction, and a second stable position, in which the connecting sections are located at a maximum mutual distance along the extension direction, wherein in passing between the first stable position and the second stable position, each bistable cell passes through an unstable equilibrium position, wherein each bistable cell is characterized by an asymmetric behavior, requiring more energy in the passage from the second stable position to the first stable position than in the passage from the first stable position to the second stable position, wherein the first connection section and the second connection section are configured to connect the respective cell indifferently to the first connection section of another cell or to the second connection section of another cell or to the first or to the second support frame (in other words, the first connection section and the second connection section are configured to connect, for example directly or via an intermediate connection element, the respective cell, to the first or second connection section of a other cell and to the first or second support frame), by means of a snap-fit connection removable even without the use of tools, in which said first and second cells independently connect the first and second support frames to each other, and the variation of the position between the first stable position and the second stable position of said cells causes a variation, along said extension direction, of a mutual distance of the first support frame from the second support frame.

[0018] In this way, an extensible structure is made available which is robust thanks to the support frames, efficient and whose cross section can be constant, as the extension does not take place using telescopic elements.

[0019] It should be added that the aspect of asymmetry is evidently advantageous if we consider that the passage from the second position to the first, that is a compression of the bistable cells, can be performed on Earth, while the passage from the first position to the second position can be performed in an extraterrestrial environment or in any case in conditions where there is little energy availability.

[0020] Thanks to the removable connection, the extensible structure is modular, reconfigurable and the cells can be reused in other structures of the same type and / or be easily replaced, without necessarily using tools.

[0021] According to an aspect of the invention, the plurality of bistable cells can comprise a first group of cells, of which the first bistable cell is part, connected to each other in series at the respective connection sections and aligned with each other along the respective directions of extension, and a second group of cells, of which the second bistable cell is part, connected to each other in series in correspondence with the respective connecting sections and aligned with each other along the respective extension directions, and in which the cells of the first group are connected to the first support frame and to the second support frame and the cells of the second group are connected to the first support frame and to the second support frame, independently of the cells of the first group.

[0022] In this way it is possible to increase the maximum distance between the first support frame and the second support frame.

[0023] In this way the extensible structure is modular, reconfigurable and the cells can be reused in other structures of the same type and / or be easily replaced, without necessarily using tools.

[0024] According to yet another aspect of the invention, the first support frame and the second support frame can be shaped as annular bodies and the extensible structure is a tubular containment structure.

[0025] In this way, a particularly resistant extensible containment structure is made available, thanks to the annular bodies, if it is pressurized in such a way that the internal pressure in an internal housing volume that the tubular structure itself defines is greater than the pressure of an external environment in which the structure is inserted, as a result of which there is a radial thrust on the structure that goes from the inside to the outside.

[0026] According to a further aspect of the invention, the aforementioned frames shaped as annular bodies of the extensible structure can be constituted by various portions held together by rigid fastening elements configured to block a relative movement between the said portions., for example said rigid fastening elements being fixed in a removable manner, preferably by means of removable or quick release or snap-fit connections, to said support frames.

[0027] In the illustrated embodiment such rigid fastening elements may not touch the bistable cells. In the illustrated embodiment, each rigid fastening element can include a first connection section configured to create a connection ( for example rigid) with the first portion of the support frame, and a second connection section configured to create a connection (for example rigid) with the second portion of the support frame.

[0028] According to one aspect of the invention, the extensible structure can include a retaining element (for example forming part of the fastening elements) connected to the first support frame and to the second support frame and fixed to them, which retaining element limits a maximum distance, for example only a maximum distance, between said first and second support frames along the extension direction.

[0029] Thanks to this solution, again in the case in which the containment structure is pressurized and is located in an external environment with lower pressure, the structure, although light, extensible and modular, is able to effectively support the longitudinal forces acting on the structure, i.e. substantially parallel to the direction of extension of the bistable cells

[0030] According to another aspect of the invention, in addition to the holding element, a second holding element can be present, which connects the first support frame and the second support frame to each other from sides of the latter which are opposite to sides of the same connected by the first retaining element, and in which the second retaining element determines a maximum distance between the sides of the supporting frames that it connects, lower than a maximum distance determined by the first retaining element between the sides of the supporting frame that it connects connect.

[0031] In this way, when at least part of the bistable cells is in the second stable position, it is possible to create a structure that follows a curved path, by virtue of the mutual approach of the first and second major support frames in correspondence with the second holding element compared to where the first holding element is positioned.

[0032] To further improve the modularity of the structure, in addition to the bistable cells that can be connected to each other via the connecting sections, another aspect of the invention can contribute, according to which the first support frame and the second support frame can each comprise a plurality of base bodies fixed removably to each other, optionally through removable and / or quick release interlocking connections.

[0033] According to one aspect of the invention, the extensible structure can comprise a plurality of rigid plate-like covering elements, which can be removably connected to the first and second support frames and collectively form a tubular wall for the internal covering of the tubular extensible structure.

[0034] Thanks to this solution it is possible to make the structure more rigid when it is brought into an extended position and also allows the use of a lining bag to create a pressurized atmosphere inside the structure.

[0035] The invention also makes available a bistable cell equipped with a first connection section and a second connection section movable with respect to each other along an extension direction, said bistable cell being movable between a first stable position, in which the connecting sections are located at a minimum mutual distance along the extension direction, and a second stable position, in which the connecting sections are located at a maximum mutual distance along the extension direction, in which the first connecting section and the second connection section are configured to make the cell connectable indifferently to the connection section of another cell or to a support frame.

[0036] According to an aspect of the invention, the first connecting section and the second connecting section are configured to create, or create, with the first and second support frames, and / or with the first or second connecting section of a the other cell, a removable connection, optionally a removable interlocking and / or quick release connection, or they are part (half) of a removable, optionally removable interlocking and / or quick release connection.

[0037] According to yet another aspect of the invention, the bistable cell can be of the type based on the Von Mises truss principle. resilient

[0038] The invention may further provide that the bistable cell may comprise

[0039] - a third beam and a fourth beam, rigid, each equipped with a first longitudinal end and a second longitudinal end, in which the respective first longitudinal ends are hinged to each other at the second connection section and the second longitudinal ends are hinged respectively, for the third beam to a (rigid) body to which the second end of the first beam is also hinged, and for the third beam to a second (rigid) body to which the second end of the second beam is also hinged, and in which the resilient element is connected to the first and second bodies and generates a force in the direction of mutual approach of said first and second bodies.

[0040] For example, the resilient element can be a strip of reduced thickness provided with portions wrapped with respect to one or more axes of curvature which are parallel to the direction of extension.

[0041] According to one aspect of the invention, bistable cells are based on the operation of the von Mises Truss and are therefore characterized by non-linear resilience and a snap switching between a compressed state and an expanded state.

[0042] According to an aspect of the invention, the extensible structure can include one or more actuators configured to act on the cells by moving the first connection portion and the second connection portion apart from each other, or on the first support frame and second support frame by moving them away from each other. Such actuators could be in the form of SMA (shape memory alloys), or actuators driven by servo motors. Such actuators can advantageously be relatively small and not very powerful, as they must provide sufficient energy to bring each cell from the first stable position to an unstable equilibrium position which is located between the first stable position and the second stable position and subsequently just overcome this point. of equilibrium going towards the second stable position, then the energy stored by the resilient element brings the cell to the second stable position. Depending on the nature of a bistable cell based on the principle of the Von Mises truss, once the point of unstable equilibrium has passed in which it is the same potential energy accumulated in the cell that allows the continuation of the extension automatically towards the second position.

[0043] Since the cell is of the asymmetric type, demanding less energy to go from compressed state to extended state than from extended state to compressed state, the size of any actuators can be further reduced.

[0044] The invention also makes available a method for obtaining a tubular structure equipped with the first support frame and the second support frame and at least two bistable cells, which follows a curved path. This method includes the step of bringing the bistable cells to the second stable position, and subsequently applying the first retaining element and the second retaining element, bringing the cells proximal to the second retaining element from the second stable position towards the first stable position.

[0045] In the event that the retaining elements are hollow, the cable of the second retaining element is pulled and / or shortened by bringing the first support frame and the second support frame that this cable connects closer together.

[0046] It is also believed that a bistable cell, in which the connection sections can be, or not, configured to allow removable connections, may be worthy of protection in its own right, in particular said cell comprising a first section, for example rigid, and a second section, for example rigid, movable with respect to each other along an extension direction, said bistable cell being movable between a first stable position, in which the sections are at a minimum mutual distance along the extension direction, and a second stable position, in where the sections are at a maximum mutual distance along the extension direction, said bistable cell also comprising:

[0047] - a first beam and a second beam, rigid, each equipped with a first longitudinal end and a second longitudinal end, in which the respective first longitudinal ends are hinged to each other at the first section and the second longitudinal ends are rotatable with respect to the second section, and

[0048] - a resilient element which generates a force in the direction of mutual approach of the second longitudinal ends of said beams, i.e.

[0049] According to one aspect of the invention, the bistable cell can comprise: - a third beam and a fourth beam, rigid, each equipped with a first longitudinal end and a second longitudinal end, in which the respective first longitudinal ends are hinged to each other at the second section and the second longitudinal ends are hinged respectively, for the third beam to a (rigid) body to which the second end of the first beam is also hinged, and for the third beam to a second (rigid) body to which the second end of the second beam is also hinged, and in which the resilient element it is connected to the first and second bodies and generates a force in the direction of mutual approach of these first and second bodies.

[0050] For example, the resilient element can be a strip of reduced thickness provided with portions wrapped with respect to one or more axes of curvature which are parallel to the direction of extension.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is an axonometric view of a bistable cell according to the invention, represented in a second stable position.

[0053] Figure 2 is an axonometric view of the cell of figure 1, represented in a first stable position.

[0054] Figure 3 is a diagram designed to explain the energy asymmetry between the first stable position and the second stable position. In particular, this graph shows a deformation length on the abscissa and a force on the ordinate. In detail, F indicates the force applied axially to the cell and d indicates the crushing of the cell, normalized to the length of a plurality of beams with which the cell is equipped. The shaded areas highlight the work required to expand the cell and the trapped energy. The graph distinguishes three regions of the stress-strain characteristic: in the first region, called Initial Positive Rigidity, the cell behaves "almost resiliently": the reaction to deformation increases with the deformation, even if in a non-linear way. In the second region, called Negative Rigidity, as the deformation increases the reaction decreases, until it becomes negative, once an unstable equilibrium point is passed. The third region, called Secondary Positive rigidity, is only theoretical.

[0055] Figure 4 is an axonometric view of an extensible structure according to the invention, represented in a retracted configuration.

[0056] Figure 5 is an axonometric view of the extensible structure of Figure 4, depicted in a partially extended configuration.

[0057] Figure 6 is an axonometric view of a support frame of the extensible structure of figures

[0058] 4 and 5. Figure 7 is an axonometric view of part of a support frame of another embodiment of support frame with respect to that of Figures 4-6.

[0059] Figure 8 is an axonometric view of another embodiment of the extensible structure according to the invention, which is equipped with the support frame partially represented in figure 7. In figure 8 the extensible structure is depicted in a retracted condition.

[0060] Figure 9 is an axonometric view of the extensible structure of Figure 8, shown in an extended configuration and in which a window or porthole frame has been installed.

[0061] Figure 10 is an axonometric view of the extensible structure of Figure 8, depicted in an extended and curved configuration.

[0062] Figure 11 is an axonometric view of a module according to the invention, equipped with the extensible structure of figures 8-10.

[0063] Figure 12 is a schematic, partially exploded view of a portion of the module of Figure 11.

[0064] Figure 13 is the same portion of the module as Figure 12 in which an external covering has been removed.

[0065] DETAILED DESCRIPTION OF THE INVENTION

[0066] The present invention will now be described, by way of illustration, but not by way of limitation, according to its preferred embodiments, with particular reference to the attached figures.

[0067] In detail, reference number 1 indicates a containment module for the containment of things and / or living beings, for example for residential or warehouse or production or agricultural or livestock use, preferably configured to be installed in the outer space, for example on an orbital station, or on an extra-terrestrial planet.

[0068] This module includes an extensible structure 15a, 15b which can be operated at least between a retracted configuration and an extended configuration.

[0069] With particular reference to figures 11-13, the module can also include an external covering, for example under an external sheet 5 and / or panels and / or regolith 10 and / or other granular / earthy material, which external covering is supported from the extensible structure 15a, 15b and is fixed (at least partially) to it, for example in a removable way.

[0070] In particular, the extensible structure of the embodiment 15b is a tubular extensible structure, which extends, for example only, along one of its axial directions. However, this does not exclude that the extensible structure could for example be a specific part of a containment structure, or of the module, such as for example an extensible wall, and / or an extensible ceiling, and / or an extensible floor, or a dividing body extensible having a rectangular or square crosssection (with respect to an extension direction of the structure) (as may be the embodiment indicated by 15a), equipped with the characteristics claimed in claim 1.

[0071] The external covering can for example cover externally, or radially, this extensible structure, whether it is tubular or not. As anticipated above, the covering can be configured to be removably connected to the extensible structure, in particular when the latter is in the extended configuration, or in a fully extended configuration. In the case of regolith or other earthy granular material, it is deposited on and / or around the structure when it is in an extended configuration, i.e. in a fully extended configuration.

[0072] In addition to the external covering, the module may include one or more access doors 20 and / or one or more portholes / windows 25 configured to be fixed, for example in a removable manner to the extensible structure 15a, 15b.

[0073] Inside the module 1, it can include an internal lining configured to delimit an internal environment of the module itself, in which internal environment the things and / or living beings that the module is configured to house are stationed. The internal lining can include a plurality of rigid panels 30, for example equal to each other, connected in a removable way to the extensible structure 15a, 15b, and / or to each other, in particular when this is in the extended configuration, or in a configuration fully extended.

[0074] Additionally, the module may comprise a pressurization bag 35 configured to retain a pressurization gas within the module and for example configured to be connected to a pressurization module. This pressurization pocket is located, for example, internally with respect to the rigid panels 30.

[0075] The internal lining may also include internal lining panels 36 which substantially line the pressurization bag and / or the rigid panels 30.

[0076] Furthermore, the internal lining can include a plurality of panels that create a floating floor 37. A space under the floating floor can be used to house pipes, electrical cables, ECLS (Environmental Control and Life Support system), etc.

[0077] Returning to the extensible structure 15a, 15b, it includes a plurality of support frames 40a, 40b, 45a, 45b, 50a, 50b, 55a, 55b, 60a, 60b, 65b, in particular rigid, for example at least a first support frame 40a, 40b and a second support frame 45a, 45b, to which the external covering and / or the door and / or the window / porthole 25 and / or the internal covering are fixed, preferably directly. In the case of the porthole / window, a frame thereof may itself be a part of the supporting support frames. In broader terms, the extensible structure or module can comprise a plurality of fastening elements, in particular rigid ones, configured to limit the mutual distance, i.e. a maximum and / or minimum distance, between the support frames of the plurality of support frames support of the extensible structure, in particular at least between the first support frame 40a, 40b and the second support frame 45a, 45b. In other words, the fasteners are configured to block relative movement between the support frames, i.e. at least between the first support frame and the second support frame.

[0078] These fastening elements are connected to the support frames 40a, 40b, 45a, 45b, 50a, 50b, 55a, 55b, 60a, 60b, 65b when the extensible structure 15a, 15b is in the extended configuration and can for example be at least one, or a combination of at least two, including: the external covering, the hatch, the window / porthole 25, the internal covering 35 and one or more retaining elements, which will be described below as they may have a further function with respect to to blocking and / or limiting the mutual position between support frames when the extensible structure is in the extended position.

[0079] Preferably, said rigid fastening elements can be connected in a removable manner, for example by means of removable interlock or quick-release or snap-fit connections, to the support frames.

[0080] Regardless of the exact elements that may be connected to the support frames 40a, 40b, 45a, 45b, 50a, 50b, 55a, 55b, 60a, 60b, 65b, each support frame of the plurality of support frames may comprise a first face 70a, 70b, or a first major and connection face 70a, 70b, for example substantially planar, and an opposite second face 75a, 75b, or a second major and connection face 75a, 75b, for example substantially planar and parallel to the first face 70a, 70b.

[0081] In the case of the extensible structure 15a, the support frames 40a, 45a, 50a, 55a, 60a are substantially rectangular, that is, the first major face 70a and the second major face 75a are substantially rectangular. In the case of the extensible structure 15b, the support frames 40b, 45b, 50b, 55b, 60b, 65b each develop along a respective closed loop path, i.e. the first major face 70b and the second major face 75b develop along a path closed in a ring. In further detail, said faces develop along a closed annular path defined by the perimeter of a rectangle or square with rounded edges. It is not excluded that in alternative not illustrated embodiments the ring path could for example be circular, or elliptical, or rectangular with edges, or of other shapes.

[0082] First face 70a, 70b and second face 75a, 75b of each support frame are connected to each other by an external perimeter edge which follows a perimeter of said faces and which is transversal, for example perpendicular, to a lying plane of said faces.

[0083] When the support frames are annular, the first faces 70b and the second faces 75b are also connected to each other by an internal perimeter edge, which is also annular.

[0084] Preferably a distance between the first face and the second face of each support frame defines a thickness of the respective support frame, which is for example a reduced thickness, i.e. each support frame can be shaped as a rigid element with reduced thickness, that is, as a flattened body, in particular a flattened and planar body. In further detail, each support frame can be shaped as a rigid plate-like (planar) body or a rigid (planar) lattice whose size develops mainly along two development directions orthogonal to each other.

[0085] The plurality of support frames 40b, 45b, 50b, 55b, 60b, 65b, or at least the first support frame 40b and the second support frame 45b, can each comprise, or can each be made up of, a plurality of bodies of base 80b, 85b, for example with reduced thickness (i.e. plate-like or reticular mainly developed along two development directions orthogonal to each other), removably fixed to each other, optionally by means of removable interlocking or quick release or snap-fit connections shot. In particular, said connections are located along an external perimeter of the base body itself.

[0086] Each support frame 40b, 45b, 50b, 55b, 60b, 65b can for example be modular, i.e. the base bodies 80b, 85b which it comprises are configured to be connectable, in particular rigidly, i.e. without residual degrees of freedom, to each other so as to be able to create frames of different shapes and / or sizes starting from the same basic bodies, so that for example it is possible to standardize the production of the basic elements for the support frames and it is possible to modify or repair an extensible structure by portions of support frame taken from another extensible structure. Furthermore, the basic bodies can all be equal to each other, or be divided into one or more types of basic bodies, wherein within each type the basic bodies are equal to each other and can be connected to the basic bodies of the others typologies. All base bodies are equipped with connection portions for connection to other base bodies compatible with such connection portions. The basic bodies can be connected to each other directly or via intermediate connection elements.

[0087] In further detail, as mentioned above, the base bodies 80b, 85b can be bodies with reduced thickness, in particular flattened reticular bodies or plate-like bodies equipped with large lightening through slots which occupy more than half of the base body itself, and they can present a first major face and an opposite second major face, which together with the other major faces of the other base bodies of the same support frame create the respective first face 70b and second face 75b. These first and second major faces can have the shape of various two- dimensional geometries, for example they can be rectangular or square or circular or circular crowns or sectors of circular crowns.

[0088] In the illustrated embodiment, the support frames 40b, 45b, 50b, 55a, 55b, 60b, 65b each comprise a plurality of base bodies, of which a plurality of first base bodies 80b and a plurality of second base bodies 85b, where in particular the first base bodies 80b are equal to each other and the second base bodies 85d are equal to each other and different from the first base bodies 80b.

[0089] In the first base bodies 80b the major faces are rectangular and each base body includes an external perimeter edge equipped with four minor faces, substantially planar, two by two parallel to each other and perpendicular to the other two, of which at least two of said minor faces which are located opposite each other (i.e. not adjacent to each other) are equipped with connection portions for connection to other base elements.

[0090] In the second base bodies 85b the first and second major faces follow a curved path, for example subtended by an angle of approximately 90°. In detail, the first and second major faces are substantially shaped like sectors of circular crowns. In this case an external perimeter edge that connects said major faces includes four minor faces, of which two rectilinear faces opposite to each other (i.e. not adjacent to each other) and lying on respective planes perpendicular to each other, and two curvilinear faces, for example that follow a path defined by a sector of the circumference. In this configuration, the connection portions for connection to other base elements are for example in the two rectilinear faces perpendicular to each other.

[0091] Overall, the ring support frame 40b, 45b is obtained by alternately connecting first base bodies with second base bodies until the ring closes on itself, as clearly visible in figures 7-10. To obtain a support frame higher and / or wider than the one illustrated in these figures, it is sufficient to insert, between two second base bodies, two or more first base bodies in series with each other, so as to substantially lengthen vertical portions and / or or horizontal ones of the support frame.

[0092] Preferably, the connection between the base bodies is removable, in particular it is removable interlock or quick-release or snap-fit. Regardless of the exact connection used, if it introduces deformations, such as the interlocking connection (interference connection) or quick release, these deformations must be solely resilient or in any case mainly resilient, in order to allow the reusability of the connection for at least a plurality of times.

[0093] In the illustrated embodiments, with particular reference to figure 7, the connection is of the "press button" type and includes a protruding body 90, for example equipped with a free rounded and / or spheroidal and / or ellipsoidal end, rigidly connected to a base body 80b, 85b and which protrudes from it, in particular which protrudes from a point on its external perimeter edge, and which is inserted by interference (deforming only resiliently) into a hole 95 made in another base body 80b, 85b or in an intermediate connection element 91.

[0094] In the portions of the first base body 80b and second base body 85b proximal to each other it is possible to observe, in particular on the first base body, a plurality of protruding bodies 90 and a plurality of holes 95, in particular positioned in one of the minor faces of the external perimeter edge. These protruding bodies 90 can be inserted into the holes 95 of the other body, in the event that these are resiliently deformable and the intermediate connection element is not present. If the intermediate connection element 91 is present, this has at least two resiliently deformable holes 95, one of which is for the insertion of a protruding body of the first base body 80b, and one for the insertion of a body protruding part 90 of the second base body 85b. In this case the holes 95 in the base bodies can be non-resiliently deformable and can be configured to simply accommodate a free end of the protruding body 90 which has passed through the hole 95 present in the intermediate connection element 91.

[0095] To separate the basic bodies joined by this connection it would be sufficient to pull them in opposite directions, overcoming the friction resulting from the resilient deformation force of the hole in which the protruding body is inserted. In particular, in applications in which the inside of a module in which the expandable structure according to the invention is implemented must be pressurized with a pressure greater than the external one, for the union of two base bodies connected to each other it is possible to envisage in addition, an obstacle connection, to prevent the two base bodies from separating due to the radial thrust from the inside towards the outside exerted by the air pressure. For this purpose, by way of example, a body configured to create an obstacle would be sufficient, for example C- or U-shaped or like a vice, straddling the sides of the external perimeter edges of two contiguous base bodies. In particular, this body can be configured to prevent the separation of the base bodies along a direction perpendicular to the faces of the external perimeter edges and to be easily removable along a direction substantially parallel to said faces.

[0096] Purely by way of example, a quick release connection could be of the type commonly used for the rapid connection of pressurizing gas or liquid pipes.

[0097] Again by way of example, a snap-fit connection could be a snap-fit mechanism, which may comprise a protuberance resiliently deformable upon bending, for example a notch fixed to a base body, and a recess, obtained in another base body, suitable to accommodate, preferably to measure, the protuberance following an approach between said base bodies and to create an obstacle connection with said protuberance after it has inserted into the recess following a resilient deformation.

[0098] It cannot be excluded that in alternative embodiments the connection between base bodies could be made using magnets, or Velcro and possibly with the aid of an obstacle connection, especially in cases where the internal pressure of the expandable structures is greater than that external.

[0099] In the illustrated embodiments, the support frames of the extensible structure 15a, 15b, or of each extensible structure 15a, 15b, are all the same, however, it cannot be excluded that in alternative embodiments they may also be different interior of a single extensible structure. In any case, as mentioned above, it is preferable that the basic bodies of each support frame are modular and / or standard compared to the other support frames of the same extensible structure and / or also other extensible structures.

[0100] The extensible structure 15a, 15b includes a plurality of bistable cells 100 interposed at least between the first support frame 40a, 40b and the second support frame 45a, 45b. For example, a plurality of bistable cells is interposed between each pair formed by two adjacent support frames. Since the configuration is the same for all the support frames and is in particular modular, in the following reference will be made mainly to the first support frame 40a, 40b, to the second support frame 45a, 45b and to the plurality of bistable cells 100 which are interposed between them.

[0101] With particular reference to figures 1 and 2, each bistable cell 100 is equipped with a first connection section 105 (i.e. a first connection body 105), in particular rigid, i.e. made up of a rigid element, and a second connection section 110 (i.e. a second connecting body 110), in particular rigid, i.e. made up of a rigid element, whose connecting sections 105,110 are movable with respect to each other along an extension direction A, i.e. along a rectilinear extension axis A.

[0102] The first connection section 105 and the second connection section 110 are configured to make the bistable cell connectable, in detail connectable in a rigid way, i.e. without residual degrees of freedom, both to the connection section of another cell and to the first or second support frame, or to make it connectable to a body equipped with a connection section compatible with the first or second connection section of the cell.

[0103] In particular, the first connection section 105 of a bistable cell 100 is configured to create a mechanical connection, in particular rigid, preferably also removable, indifferently with the first or second connection section of another cell or with a connection of a support frame, and the second connection section 110 is configured in the same way to create a mechanical connection, in particular rigid, preferably also removable, indifferently with the first or second connection section of another cell or with a connection section of a support frame. In further detail, the first connection section, the second connection section and the connection sections of the support frame are all compatible with each other, allowing a connection of the first and second connection section to any of the other sections, at condition that it is only one of these connection sections at a time, so that a first connection section of a bistable cell can selectively couple with the second connection section of another cell or with a first connection section of a another cell or with a connection section of the support frame, based on the assembly needs of the extensible structure. Furthermore, in the illustrated embodiment, the first connection section 105 and the second connection section 110 are configured to make the respective cell also connectable to the connection portions of the base bodies 80b, 85b.

[0104] With regard to the support frame, it can comprise a plurality of connection sections, to each of which the first connection section 105 or the second connection section 110 of a bistable cell 100 can be connected, in particular in a rigid manner. For example, the first support frame 40a, 40b and the second support frame 45a, 45b each comprise at least a first connection section 115 and a second connection section 120, preferably identical. In particular, each base body of the respective support frame includes at least one connection section 115, for example at least two connection sections 115,120.

[0105] The connection made by said connection sections 105,110 can be direct, or can be mediated by an intermediate connection element 111 (see the enlargement in figure 9).

[0106] The intermediate connection element 111 makes a connection similar to that made by the intermediate connection element 91.

[0107] The first connection section 105 can include a first portion, for example a first half, of a connection mechanism which has its second portion, for example a second half, which can be coupled to the first and present in another connection section (i.e. a other first connection section 105 or the second connection section 110 or the connection section 115,120 of the support frame).

[0108] In the illustrated embodiment, in order to make all the connection sections of the cells connectable to each other, each connection section (either first or second) includes both the first portion (half) of a first connection mechanism, which first portion is configured to be coupleable to a second portion (half) of the first connection mechanism forming part of another connection section (first or second or of the support frame), which the second portion (half) of a second connection mechanism, which second portion is configured to be coupled to a first portion (half) of the second connection mechanism forming part of another connection section (first or second or of the support frame), or of the other connection section which is already equipped with the second portion of the first linkage mechanism.

[0109] For example, the first and second connecting mechanisms may be identical, in the illustrated embodiment the first connecting section and the second connecting section are the same for all bistable cells 100.

[0110] In case the connection between the first connecting section and the second connecting section is direct, the first portion and the second portion constitute the connecting mechanism. In the event that the connection requires the intermediate connection element, the connection mechanism is constituted by the first portion, the second portion and the intermediate connection element, which includes a first section configured to create a stable connection with the first portion of the connecting mechanism, and a second portion configured to make a stable connection with the second portion of the connecting mechanism.

[0111] The support frame may for example include only the first portion (half) of the first connecting mechanism and / or the second portion (half) of the second connecting mechanism. However, this does not exclude that in an alternative embodiment not illustrated, the connection section of the support frame could be shaped like the first and / or second connection section of the bistable cell 100.

[0112] Since the connection sections preferably make a removable connection available, it follows that the connection mechanism is preferably of the removable type, in particular it can be of the removable interlocking or quick-release or snap-fit type. Regardless of the exact typology used, if it introduces deformations, such as for example the interlocking connection (interference connection) or quick release, these deformations must be solely resilient or in any case mainly resilient, in order to allow the reusability of the connection for at least a plurality of times.

[0113] In the illustrated embodiments, each connection mechanism is of the "press button" type and provides in the first portion, or first half, a protruding body 90 (which can be the same as the base bodies), for example equipped with a free convex and / or spheroidal and / or ellipsoidal end, and which is inserted by interference (deforming only resiliently) in a hole 95, for example a passing one, present in another connection section and with which the second portion of the mechanism is equipped connection or present in the intermediate connection element 111, or in the first or second section of the intermediate connection element 111, (if provided). In the event that the intermediate connection element 111 is present, the hole 95 present in the connection sections of the bistable cells may not be resiliently deformable, or in any case the protruding body 90 is inserted there with play. To separate the bistable cells from the support frames it is sufficient to pull the cells and frames in opposite directions, overcoming the friction resulting from the resilient deformation.

[0114] Now going into more detail about the connection sections, the first connection section 105 can include a contact surface 130, for example planar, preferably facing in the opposite direction to the second connection section 110 and transversal, or perpendicular, to the extension direction A, from which the protruding body 90 protrudes, for example as a cantilever, and which is also preferably crossed by the hole 95, which is for example arranged with the respective central axis transverse (perpendicular) to the contact surface 130. Preferably the contact surface 130 is crossed by at least two (equal) holes 95 and at least two (equal) protruding bodies 90 protrude from it, for example cantilevered.

[0115] Similarly, the second connection section 110, which can be the same as the first connection section 105, includes a contact surface (not visible in the figures), for example planar, preferably facing in the opposite direction to the first connection section 105 and transverse, that is, perpendicular to the extension direction A, from which the protruding body 90 protrudes, for example as a cantilever, and which is crossed by the hole 95, which is for example arranged with the respective central axis transverse (perpendicular) to the contact surface. Preferably the contact surface is crossed by at least two (equal) holes 95 and at least two (equal) protruding bodies 90 protrude from it, for example cantilevered.

[0116] Protruding bodies 90 and holes 95 in the connection sections are positioned so that it is possible to attach a second connection section or even a first connection section to a first connection section. For example, the two protruding bodies 90 are diametrically opposed with respect to an axis parallel to the extension direction A and passing through a central position of the first section and the second section, that is, they are diametrically opposed with respect to the extension direction A, and the two holes 95 are arranged are diametrically opposite with respect to this axis and are aligned along an alignment direction orthogonal to a direction along which the protruding bodies are aligned, which alignment direction of the protruding bodies is for example orthogonal to the extension direction A.

[0117] In the case of the connection sections 115,120 of the support frame, as clearly visible in the enlargement of figure 6, these connection sections include a support surface 140, for example planar, which is crossed by the hole 95, for example by at least two holes 95, preferably from four holes 95 whose central axes fall in the vertices of a square lying on the support surface 140 itself. The connecting sections of the support frame do not include the protruding element. The support surface 140 is for example contacted by the contact surface 130 when a first section 105 or second section 110 is connected to the connection section 115,120.

[0118] It cannot be excluded that the connection mechanism could be different, for example in the case of the quick release connection it could be of the type commonly used for the quick coupling of pipes pressurized by gas or liquid. Still by way of example only, a snap-fit connection could be a snap-fit mechanism, which may comprise a protuberance resiliently deformable upon bending, for example a notch fixed to the first connection section, and a recess, obtained in the second connection section, suitable to accommodate, preferably to measure, the protuberance following an approach between said sections and to create an obstacle connection with said protuberance after it has inserted into the recess following a resilient deformation. Furthermore, the connection between connecting sections could be made using magnets or Velcro.

[0119] Regardless of the exact connecting mechanism, the first and second connecting sections may include recesses configured to facilitate insertion of hands or a bladed tool between joined connecting sections in order to more easily detach them. This hollow in particular starts from a perimeter edge of the connection section, for example crosses the contact surface of the connection section, and leans towards a central area of the connection section.

[0120] Each bistable cell 100 is movable between a first stable position, in which the connecting sections 105,110 are located at a minimum mutual distance along the extension direction, and a second stable position, in which the connecting sections 105,110 are located at a distance maximum reciprocal along the extension direction. In particular, in the passage from the first stable position to the second stable position, upon reaching a predetermined mutual distance between the connection sections 105,110, the bistable cell finds itself in an unstable equilibrium position, in which a very small force, i.e. an arbitrarily small force, , can trigger an automatic reaching of these stable positions by the bistable cell itself, i.e. it can trigger an automatic reaching of said first and second stable positions by the bistable cell itself. In other words, when a bistable cell 100 is in the unstable equilibrium position, it automatically reaches the first stable position or the second stable position depending on whether an arbitrary small force is applied to the same cell, along the extension direction A, respectively, in a direction of mutual approach or separation of said connecting sections 105 and 110.

[0121] The first stable position may define a compressed condition of the bistable cell 100, while the second stable position may define an extended condition of the bistable cell 100.

[0122] Each bistable cell 100 is of the type based on the Von Mises truss principle, for example of the asymmetric type requiring greater energy in the passage from the second stable position to the first stable position than in the passage from the first stable position to the second stable position (as represented in the graph of figure 3). That is, more energy is required in the transition from the second stable position to the unstable equilibrium position than in the transition from the first stable position to the unstable equilibrium position. Regardless of asymmetry or not, bistable cells based on the Von Mises truss principle can be defined as groups of elements characterized by an accumulation and release of nonlinear resilient potential energy and by a snap switching between a compressed state and an expanded state, which states correspond to the first stable position and the second stable position, respectively.

[0123] Each bistable cell 100 can comprise a first beam 150, rigid (and for example monolithic), equipped with a first longitudinal end rotatably associated, in particular directly, with the first connection section 105, and a second longitudinal end, opposite to the first, rotatable with respect to the second connection section 110, for example hinged to a first body, in particular rigid, 155 which in turn is connected to the second connection section 110.

[0124] The first body 155 can be at least partially, preferably entirely, interposed between the first connection section and the second connection section when the bistable cell is in the second stable position. In detail, the first body 155 can be at least partially, preferably entirely, interposed between a plane perpendicular to the extension direction A and which intersects the first connection section 105 and a plane perpendicular to the advancement direction A and which intersects the second connection section connection 110, when the bistable cell is in the second stable position.

[0125] The first longitudinal end of the first beam 150 can for example be hinged to the first connection section 105 with respect to a first hinge axis lying on a plane orthogonal to the extension direction A and the second end can be hinged to the first body 155 according to a second hinge axis parallel to the first hinge axis.

[0126] Each bistable cell 100 can also include a second beam 160, rigid (and possibly monolithic), for example having a longitudinal extension equal to the first beam 150, equipped with a first longitudinal end rotatably associated, in particular directly, with the first connection section 105, and a second longitudinal end, opposite to the first, rotatable with respect to the second connection section 110, for example hinged to a second body, in particular rigid, 165 which in turn is connected to the second connection section 110. The first longitudinal end can for example be hinged to the first connection section 105 with respect to a first hinge axis lying on a plane orthogonal to the extension direction A, preferably said first hinge axis being eccentric to the first hinge axis of the first beam 150 and lying on the same plane perpendicular to the extension direction A. The second end of the second beam 160 can be hinged to the second body 165 according to a second hinge axis parallel to the first hinge axis.

[0127] Like the first body 155, the second body 165 can be at least partially, preferably entirely, interposed between the first connection section 105 and the second connection section 110 when the bistable cell is in the second stable position. In detail, the second body 165 can be at least partially, preferably entirely, interposed between a plane perpendicular to the extension direction A and which intersects the first connection section 105 and a plane perpendicular to the advancement direction A and which intersects the second connection section connection 110, when the bistable cell is in the second stable position.

[0128] Each bistable cell 100 includes a resilient element 170 which generates a force in the direction of mutual approach of the second longitudinal ends of said first beam 150 and second beam 160, in particular this resilient element 170 generates a force in the direction of mutual approach on the first body 155 and on the second body 160. In further detail, the resilient element 170 is the only means of connecting the second longitudinal ends to each other and the first and second bodies 155,165 to each other. Without this resilient element the second ends of the beams and the first and second bodies would be free to move with respect to each other.

[0129] In the second stable position, the first beam and the second beam are arranged with their respective longitudinal axes inclined with respect to the extension direction A and with each other, in particular to form an angle between them which can be acute or obtuse.

[0130] When the first connection section 105 is pushed towards the second connection section, the resilient element 170 is pulled by the first and second bodies, which move away from each other depending on the fact that the beams are rigid and go towards a condition in which they are aligned with each other, therefore they occupy a greater longitudinal space than when they are both inclined between each other and with respect to the direction of extension A. Until the unstable equilibrium position is reached, which corresponds to a position in the where the first beam and the second beam are arranged with their respective longitudinal axes parallel to each other and perpendicular to the extension direction A, it is necessary to provide thrust to the bistable cell 100 by pushing the first connection section 105 towards the second connection section 110. Passed the point of unstable equilibrium, the resilient force of the resilient element 170 is sufficient to bring together the second longitudinal ends of the beams or the first and second bodies 155,165, as a result of which force the first connecting section is automatically moved towards the second connecting section connection and the first stable position.

[0131] The first stable position is defined by an abutment surface 175 against which the first beam 150 or the second beam 160 or the first connection section abuts under the action of the resilient element when the first connection section moves from the unstable equilibrium position towards the first stable position.

[0132] In particular, this abutment surface 175 is made available by the first body 155, and limits the rotation of the first beam 150 when the first longitudinal end of the latter approaches the second connection section 110. In particular, the first beam comes into contact with this abutment surface 175 when it reaches the first stable position. This abutment surface 175 is for example a surface of the first body 155 facing the first beam and the first second connection, for example positioned near the second hinge axis. For example, there is also a second abutment surface 180, which is made available by the second body 165 and limits the rotation of the second beam 160 when the first longitudinal end of the latter approaches the second connection section. This second abutment surface 180 is for example a surface of the second body 165 facing the second beam and the second connection point, for example positioned in proximity to the second hinge axis.

[0133] This abutment surface is, or rather these abutment surfaces are, conveniently positioned so that the angle formed between the longitudinal axis of the first and second beam with respect to a plane perpendicular to the extension direction A, when the cell bistable cell is found in the first stable position is smaller, in particular at least 50% lower and of opposite sign, compared to the angle formed by the longitudinal axes of the first and second beam with respect to this plane perpendicularto the extension direction A, when the cell bistable is in the second stable position. In this way the asymmetry of the cell is achieved.

[0134] In the first stable position, the first beam and the second beam are arranged with their respective longitudinal axes inclined with respect to the extension direction A and with each other, in particular to form an angle between them which can for example be obtuse.

[0135] When the first connection section 105 is pushed away from the second connection section, the resilient element 170 is placed under tension by the first and second bodies, which move away from each other depending on the fact that the beams are rigid and move towards a condition (that of unstable equilibrium) in which they are arranged with their respective longitudinal axes aligned with each other, therefore they occupy a greater longitudinal space than when they are both inclined to each other and with respect to the extension direction A. Until upon reaching the unstable equilibrium position, it is necessary to supply energy to the bistable cell 100 by pushing the first connection section 105 away from the second connection section 110. Once the unstable equilibrium point has been exceeded, the resilient force of the resilient element 170 is sufficient to bring the second longitudinal ends of the beams together, i.e. the first and second bodies 155,165, as a result of which force the first connection section 105 is automatically moved away from the second connection section 110 and towards the second stable position.

[0136] The second stable position can also be defined by an abutment surface (not visible in the figures) against which the first beam 150 or the second beam 160 or the first connection section can abut under the action of the resilient element when the first connecting section moves towards the second stable position.

[0137] In particular, this abutment surface can be made available by the first connection section itself and limits the rotation of the first beam 150 and / or the second beam 160 when the second longitudinal end of the latter moves away from the second connection section.

[0138] One of the first and second bodies could be rigidly joined to the second connecting section, however in the preferred embodiment, the second connecting section is also joined to the first and second bodies by means of a mechanism which exploits the principle of the Von Mises truss. For example, the second connecting section is connected to the first body and second body 155,165 in the same way as the first connecting section is connected thereto. In particular, the bistable cell can include a third beam 190, rigid (and possibly monolithic), for example having the same longitudinal extension as the first beam 150, equipped with a first longitudinal end rotatably associated, in particular directly, with the second connection section 110, and a second longitudinal end, opposite to the first, rotatable with respect to the first connection section 105, for example hinged to the first body 155.

[0139] The first longitudinal end can for example be hinged to the second connection section 110 with respect to a first hinge axis lying on a plane orthogonal to the extension direction A, for example parallel and to the first hinge axis of the first beam, and the second end can be hinged to the first body 155 according to a second hinge axis parallel to the first hinge axis, for example eccentric with respect to the second hinge axis of the first beam 150.

[0140] Each bistable cell 100 can also include a fourth beam 195, rigid (and possibly monolithic), for example having the same longitudinal extension as the third beam 190, equipped with a first longitudinal end rotatably associated, in particular directly, with the second connection section 110, and a second longitudinal end, opposite to the first, rotatable with respect to the first connection section 105, for example hinged to the second body 165

[0141] The first longitudinal end of the fourth beam can for example be hinged to the second connection section 110 with respect to a first hinge axis lying on a plane orthogonal to the extension direction A, preferably said first hinge axis being parallel and possibly eccentric to the first hinge axis of the third beam 190 and lying on the same plane perpendicular to the extension direction A. The second longitudinal end of the fourth beam 195 can be hinged to the second body 165 according to a second hinge axis parallel to the first, for example eccentric with respect to the second hinge axis of the second beam 160.

[0142] Each bistable cell 100 can include a further resilient element which generates a force in the direction of mutual approach of the second longitudinal ends of said third beam 190 and fourth beam 195, or the resilient element 170 which generates a force in the direction of mutual approach is sufficient on the first body 155 and on the second body 160.

[0143] In the second stable position, the third beam and the fourth beam are arranged with their respective longitudinal axes inclined with respect to the extension direction A and with each other, in particular to form an angle between them which can be acute or obtuse. Therefore, in this position along the extension direction we meet in the following sequence the first connecting section, the first and second beam at the same time, the first body and the second body at the same time, the third and fourth beam at the same time, and finally the second connecting section.

[0144] When the first connection section 105 and the second connection section 110 are pushed towards each other, the resilient element 170 is placed under tension by the first and second bodies, which move away from each other in function of the fact that all the beams are rigid and move towards a condition in which they are aligned with each other, therefore they occupy a greater longitudinal space than when all four are inclined between each other and with respect to the extension direction A. Until reaching the position of unstable equilibrium, which corresponds to a position in which the first beam and the second beam are arranged with their respective longitudinal axes parallel to each other and perpendicular to the extension direction A, and in which the third beam and the fourth beam are arranged with the respective longitudinal axes parallel to each other and perpendicular to the extension direction A, it is necessary to supply energy to the bistable cell 100 by bringing the first connection section 105 and the second connection section 110 closer together in contrast to the force exerted by the resilient element. Once the point of unstable equilibrium has been exceeded, the resilient force of the resilient element is sufficient to bring the second longitudinal ends of all the beams closer together, or to bring the first and second bodies 155,165 closer together, as a result of which it forces the first connection section and the second connection section are automatically moved towards each other and towards the first stable position.

[0145] For the definition of the first stable position, as regards the third beam and fourth beam, as in the case of the first stable position of the first beam and the second beam, the cell can include a bearing surface (not visible in the figures) against which the first beam 150 or the second beam 160 or the first connection section comes into contact under the action of the resilient element when the second connection section moves from the unstable equilibrium position towards the first stable position.

[0146] In particular, this abutment surface is made available by the first body 155, and limits the rotation of the third beam 190 when the first longitudinal end of the latter approaches the first connection section. In particular, the third beam comes into contact with this abutment surface when it reaches the first stable position. This abutment surface is for example a surface of the first body 155 facing the third beam and the first connection point, for example positioned near the second hinge axis. For example, there is also a second abutment surface (not visible in the figures), which is made available by the second body 165 and limits the rotation of the fourth beam 195 when the first longitudinal end of the latter approaches the first connection section. This second abutment surface is for example a surface of the second body 165 facing the fourth beam and the first connection point, for example positioned near the second hinge axis.

[0147] This abutment surface is, or rather these abutment surfaces are, conveniently positioned(s) so that the angle formed between the longitudinal axis of the third and fourth beam with respect to a plane perpendicular to the extension direction A, when the cell bistable cell is found in the first stable position is smaller, in particular at least 50% lower, than the angle formed by the longitudinal axes of the third and fourth beam with respect to this plane perpendicular to the extension direction A, when the bistable cell is found in the stable second position. In this way the asymmetry of the cell is achieved.

[0148] In the first stable position, the fourth beam and the third beam are arranged with their respective longitudinal axes inclined with respect to the extension direction A and with each other, in particular to form an angle between them which can for example be obtuse.

[0149] When the first connection section 105 and the second connection section are pulled in the direction of moving away from each other, the resilient element 170 is placed under tension by the first and second bodies, which move away from each other due to the fact that the beams are rigid and move towards a condition (that of unstable equilibrium) in which they are aligned with each other, therefore they occupy a greater longitudinal space compared to when they are both inclined to each other and with respect to the direction of extension A. Until the unstable equilibrium position is reached, it is necessaryto supply energy to the bistable cell 100 by moving the connecting sections apart. Once the point of unstable equilibrium has been exceeded, the resilient force of the resilient element 170 is sufficient to bring the second longitudinal ends of the beams together, i.e. the first and second bodies 155,165, as a result of which force the first connection section is automatically moved away from the second connection section 110 and towards the second stable position.

[0150] Even the second stable position, as regards the third and fourth beam, can be defined by an abutment surface (not visible in the figures), also in this case it can be made available by the connection section, or by the second connection section.

[0151] Alternatively or in addition to the third and fourth beams, each bistable cell can comprise another pair of beams in addition to the first beam and the second beam, for example a fifth beam 200 and a sixth beam 205, which beams of the other pair of beams substantially replicate the configuration of the first beam and the second beam being hinged to the first connection section 105 and to the first body and second body, but they are hinged to this first connection section 105 with respect to hinge axes perpendicular to those of the first beam and second beam and a resilient element acts on them which generates a force perpendicular to the resilient element which brings the first beam and the second beam closer together, although in the illustrated embodiment, the result is obtained from a single resilient element or resilient group that generates an approaching force in both directions.

[0152] In detail, each bistable cell 100 can comprise, alternatively or in addition to the third and fourth beam, a fifth rigid beam 200, for example having a length equal to the first beam 150 and preferably arranged with its longitudinal axis lying on a plane perpendicular to a plane containing the longitudinal axis of the first beam and the extension direction A. The fifth beam 200 is equipped with a first longitudinal end rotatably associated, in particular directly, with the first connection section 105, and a second longitudinal end, opposite to the first, rotatable with respect to the second connection section 110, for example hinged to a third body, in particular rigid, 210 which in turn is connected to the second connection section 110.

[0153] The third body 210 can be at least partially, preferably entirely, interposed between the first connection section and the second connection section when the bistable cell is in the second stable position. In detail, the third body 210 can be at least partially, preferably entirely, interposed between a plane perpendicular to the extension direction A and which intersects the first connection section 105 and a plane perpendicular to the advancement direction A and which intersects the second connection section connection 110, when the bistable cell is in the second stable position.

[0154] The first longitudinal end of the fifth beam 200 can for example be hinged to the first connection section 105 with respect to a first hinge axis lying on a plane orthogonal to the extension direction A and perpendicular to the first hinge axis of the first beam 150. The second end can be hinged to the third body 210 according to a second hinge axis parallel to the first hinge axis of the fifth beam 200.

[0155] Each bistable cell 100 can also include a sixth rigid beam 205, for example having a longitudinal extension equal to the fifth beam 200, equipped with a first longitudinal end rotatably associated, in particular directly, with the first connection section 105, and a second longitudinal end, opposite to the first, rotatable with respect to the second connection section 110, for example hinged to a fourth body, in particular rigid, 215 which in turn is connected to the second connection section 110. The first longitudinal end can for example be hinged to the first connection section 105 with respect to a first hinge axis parallel and eccentric to the first hinge axis of the fifth beam 200 and lying on the same plane perpendicular to the extension direction A. The second end of the sixth beam 205 can be hinged to the fourth body 215 according to a second hinge axis parallel to the first hinge axis of the sixth beam itself.

[0156] Like the third body 210, the fourth body 215 can be at least partially, preferably entirely, interposed between the first connection section 105 and the second connection section 110 when the bistable cell is in the second stable position. In detail, the fourth body 215 can be at least partially, preferably entirely, interposed between a plane perpendicular to the extension direction A and which intersects the first connection section 105 and a plane perpendicular to the advancement direction A and which intersects the second connection section connection 110, when the bistable cell is in the second stable position.

[0157] Each bistable cell 100 can include a further resilient element, which generates a force in the direction of mutual approach of the second longitudinal ends of said fifth beam 200 and sixth beam 205, in particular this further resilient element generates a force in the direction of mutual approach on the third body 210 and on the fourth body 215. As a further detail, the further resilient element is the only means of connecting the second longitudinal ends to each other and the third and fourth bodies to each other. Without this resilient element, the third and fourth bodies would be free to move relative to each other. In the illustrated embodiment, the resilient element and the further resilient element substantially form a resilient group comprising a first resilient portion 170a which resiliently connects the first body 155 and the third body 210, generating a force on them in the direction of mutual approach, a second resilient portion 170b which resiliently connects the third body 210 and the second body 165 generating on them a force in the direction of mutual approach, a third resilient portion 170c which resiliently connects the first body 155 and the fourth body 215 generating on them they provide a force in the direction of mutual approach, and a fourth resilient portion 170d which resiliently connects the fourth body 215 and the second body 210, generating a force on them in the direction of mutual approach.

[0158] In the illustrated embodiment, each resilient portion is shaped as a ribbon of reduced thickness equipped with portions wrapped with respect to one or more axes of curvature which are parallel to the extension direction A.

[0159] It cannot be excluded that in an alternative embodiment not illustrated, the resilient element could be present in the form of a helical traction spring which extends from the first body to the second body, and the further resilient element in the form of a spring traction helical extending from the third body to the fourth body.

[0160] In the second stable position, the fifth beam and the sixth beam are arranged with their respective longitudinal axes inclined with respect to the extension direction A and with each other, in particular to form an angle between them which can be acute or obtuse.

[0161] When the first connection section 105 is pushed towards the second connection section, the resilient element 170 is pulled by the first and second bodies, which move away from each other depending on the fact that the beams are rigid and must towards a condition in which they are aligned with each other, therefore they occupy a greater longitudinal space than when they are both inclined between each other and with respect to the direction of extension A. Until the unstable equilibrium position is reached, which corresponds to a position in the where the fifth beam and the sixth beam are also arranged with their respective longitudinal axes parallel to each other and perpendicular to the extension direction A, it is necessary to provide thrust to the bistable cell 100 by pushing the first connection section 105 towards the second connection section 110. Once the point of unstable equilibrium has been exceeded, the resilient force of the further resilient element, i.e. the resilient group, is sufficient to bring the second longitudinal ends of the beams together, i.e. the third and fourth bodies 210,215, as a result of which it forces the first connection section is automatically moved towards the second connection section and the first stable position.

[0162] Similarly to the other beams, also for the fifth and sixth beam the first stable position and the second stable position are defined by abutment surfaces similarto those of the other beams, with the difference that in this case they are located on the third and fourth body. Overall, the positions, i.e. the orientations of all the beams are equal in the first stable position, in the unstable equilibrium position and in the second stable position. In other words, all the beams move synchronously with each other and the instantaneous angle formed by the longitudinal axis of any beam with respect to the extension direction A at any position between the first stable position and the second stable position is equal in magnitude to the angle formed by the longitudinal axis of any of the other beams.

[0163] One of the third body and the fourth body could be rigidly joined to the second connection section, however in the preferred embodiment, the second connection section is also joined to the third and fourth body by means of a mechanism which exploits the principle of the Von Mises truss. For example, the second connecting section is connected to the third body and fourth body 155,165 in the same way as the first connecting section is connected thereto.

[0164] In particular, the bistable cell can include a seventh beam 220, rigid, for example having the same longitudinal extension as the first beam 150, and an eighth beam 225, which connect the second section to the third and fourth body in a similar way to how the third and fourth beams connect the second connection section to the first and second bodies, with the difference that the hinge axes of the seventh and eighth beams are parallel to the hinge axes of the fifth and sixth beams.

[0165] In the illustrated embodiment, all the bistable cells 100 are equal to each other. However, it cannot be excluded that in alternative embodiments they could be different from each other with regard to the dimensions of the beams and / or the number of beams and / or the type of resilient element.

[0166] As mentioned above, the plurality of cells placed between the first support frame 40a, 40b and the second support frame 45a, 45b includes at least a first bistable cell 100 and a second bistable cell 100 which connect the first support frame to each other 40a, 40b and the second support frame 45a, 45b, and are arranged with the respective extension directions A transverse, in particular perpendicular, to the first face 70a, 70b, and to the second face 75a, 75b of said support frames.

[0167] A variation of the position between the first stable position and the second stable position of said bistable cells causes a variation, along the said extension direction, of a reciprocal distance of the first support frame 40a, 40b from the second support frame 45a, 45b.

[0168] When the first bistable cell and the second bistable cell are in their respective second stable position, the mutual distance between the first support frame and the second support frame is greater than when at least one of the two bistable cells is in the first stable position.

[0169] In particular, when all the bistable cells 100 of the plurality of bistable cells 100 are in the second stable position, i.e. in their extended configuration, the extensible structure is in its extended configuration, and when all the bistable cells 100 of the plurality of bistable cells 100 are in the first stable position, i.e. in their compressed configuration, the extensible structure is in its retracted configuration.

[0170] The first cell 100 and a second cell 100 connect, independently of each other, the first support frame 40a, 40b and the second support frame 45a, 45b, i.e. the first cell 100 is connected to the first support frame 40a, 40b and to the second support frame 45a, 45b independently with respect to the second cell 100 which in turn is connected to the first support frame 40a, 40b and to the second support frame 45a, 45b. In further detail, the first connection section 105 or the second connection section 110 of the first and second cells is connected, for example directly, to the first support frame 40a, 40b and / or to the second support frame 45a, 45b independently from the other cell. In particular, there is no direct connection between the first cell and the second cell and a transmission of stresses from one to the other can only take place via the support frames.

[0171] In further detail, in the embodiment of the extensible structure 15a illustrated in figures 4 and 5, in which each bistable cell 100 is also directly connected to both the first support frame and the second support frame, the first connection section 105 of the first cell 100 is connected to the first connection section 115 of the first support frame 40a, 40b, the second connection section 110 of the first cell 100 is connected to the first connection section 115 of the second support frame 45a, 45b, the first connection 105 of the second cell 100 is connected to the second connection section 120 of the first support frame 40a, 40b, and the second connection section 110 of the second cell 100 is connected to the second connection section 120 of the second support frame 45a, 45b.

[0172] In the illustrated embodiment of the extensible structure 15d illustrated in figures 7 onwards, the plurality of bistable cells comprises a plurality of groups of bistable cells, of which at least a first group of cells, of which the first bistable cell 100 is part, and a second group of bistable cells, of which the second bistable cell 100 is part. The bistable cells 100 of the first group are connected to the first support frame 40b and to the second support frame 45b and the bistable cells of the second group are connected to the first support frame and to the second support frame, independently of the cells of the first group. Each bistable cell group is attached to both the first support frame and the second support frame independently of the other bistable cell groups. In further detail, the cells of the first group are not directly connected to the cells of the second group, a transmission of stresses from one to the other can only occur via the support frames.

[0173] In each group the bistable cells that compose it, which for example are in equal number in each group, are connected to each other in series through the respective connection sections (directly or through the intermediate connection elements), are arranged with the respective extension directions A transverse, or perpendicular, to the first and second faces of the support frames that the group connects, for example the individual extension directions A are substantially all parallel to each other (possibly also coaxial to each other). The cells of each group are aligned with each other along their respective extension directions, essentially forming a row or a row or a column of bistable cells that extends along a single extension direction A.

[0174] In further detail, each group of bistable cells includes at least one head cell connected by its first or second connection section to the first support frame, and a tail cell connected by its first or second connection section to the second support frame, support. If there are only two bistable cells, the head cell and the tail cell are connected to each other (solely) via the respective connection sections not engaged with the support frames (directly or via the intermediate connection elements). In the case of more than two bistable cells for each group, at least a third bistable cell is placed between the head cell and the tail cell and is connected to them by means, in particular only, of its first and second connection sections (directly or by the intermediate connecting elements). In further detail, along the series of bistable cells of each group, all the bistable cells of that group, with the exception of the tail bistable cell and the head bistable cell, are connected only to the two adjacent bistable cells, i.e. to a previous cell, more close to the head cell or corresponding to it, and to a subsequent cell, closer to the tail cell or corresponding to it, and only through its own connecting sections.

[0175] In the example of the at least first and second group of bistable cells, the head cell of the first group is connected directly via its first or second connection section to the first support frame, for example to the first connection section 115 of the first frame support frame, and the tail cell is directly connected via its first or second connection section to the second support frame, for example to the first connection section 115 of the second support frame. The head cell of the second group is connected directly by its first or second connection section to the first support frame, for example to the second connection section 120 of the first support frame, and the tail cell is connected directly by its first or second connection section to the second support frame, for example to the second connection section 120 of the second support frame.

[0176] In the retracted position of the extensible structure the extension directions of the cells of each group are all parallel or possibly even coaxial with each other. Parallelism / coaxiality between the extension directions A of the cells of each group occurs as long as the extensible structure is extended along a straight direction, in the case in which the structure is curved in the manner indicated below, as illustrated in figure 10, obviously this parallelism / coaxiality is missing and the set of extension directions of each group substantially forms a curved path formed by straight segments constituted by the extension direction of each bistable cell of the single group.

[0177] As indicated at the beginning of this description, the extensible structure or module 1 can comprise one or more fastening elements, which can comprise or be constituted by one or more holding elements, in particular at least a first holding element 240, for example made in the form of a cable, in particular inextensible. Said retaining element limits, or only limits, the maximum distance between two support frames that it connects, for example the first and second support frames, or it limits the maximum distance between two portions of the two support frames that it connects at the which portions is fixed. In other words, the first retention element prevents the maximum distance from being greater than a predetermined value, and therefore prevents the bistable cells from being extended, or in any case stressed, beyond a predetermined value, therefore beyond their second stable position.

[0178] In particular, in the illustrated embodiment, the retaining element 240 directly connects only two support frames to each other and includes a first longitudinal end fixed to one (in the figure the frame 65b) of the two support frames that it connects and a second longitudinal end fixed to the other of the two supporting frames that it connects (in the figure the frame 40b), any support frames placed between the two that it connects can be crossed by the retaining element. In detail, the support frames can each be equipped with at least one through hole 250 crossed or passable by the retaining element. Such through holes are positioned in the same portion for each support frame, so that when the extensible structure is assembled and is in the retracted position, such through holes are aligned with each other. In the illustrated embodiment, the through holes 250 are made in correspondence with the connection sections 115 and 120 of the support frames. In this case the bistable cells are configured to be crossed by the retaining element. In particular, the first connection section 105 and the second connection section 110 each include a through hole 255 which when the first and second connection section 105,110 are connected to the first or second connection section 115,120, the through holes 225 are aligned with the hole 250. Furthermore, the resilient element 170 does not obstruct a line of passage between the through holes 255, for example by being more external or equipped with a slot in which the retaining element can pass freely.

[0179] Preferably, there are a plurality of first holding elements 240, which are fixed to different portions of the supporting frames that they connect. As a consequence of this, the support frames can include a plurality of through holes configured to be passed through by the first retaining elements. In addition to the first holding element 240, a second holding element 245 can be present, for example made in the shape of a cable, in particular inextensible. This second holding element 245 limits, or only limits, the maximum distance between two support frames that it connects, for example between the first and the second support frame, or rather limits the maximum distance between two portions of the two support frames that it connects in correspondence with which portions it is fixed, which portions are different from those connected by the first retaining element, for example they can be substantially diametrically opposite with respect to a central area of the support frame. The maximum distance allowed by the second holding element is lower than the maximum distance allowed by the first holding element and thanks to this it is possible to create extensible structures that follow a curved path, or in other words that do not extend along a straight line when they are in extended configuration, but rather along a curve.

[0180] Also for the second retaining element 245, in the illustrated embodiment, it directly connects only two support frames to each other and includes a first longitudinal end fixed to one (in the figure the frame 65 b) of the two support frames that it connects and a second longitudinal end fixed to the other of the two supporting frames that it connects (in the figure the frame 40b), any support frames placed between the two that it connects can be crossed by the retaining element. In detail, the support frames can each be equipped with at least one through hole 250 crossed or passable by the second retaining element 245. These through holes are positioned in the same portion for each support frame, so that when the extensible structure is assembled and is in the retracted position, these through holes are aligned with each other.

[0181] Preferably, there are a plurality of second holding elements 245, which are fixed to different portions of the supporting frames that they connect. As a consequence of this, the support frames can include a plurality of through holes configured to be passed through by the second retaining elements.

[0182] The curvature of an extensible structure is obtained by bringing the extensible structure into an extended configuration, then at least the first retaining element 240 is installed on the support frames, subsequently the second retaining element 245 is installed overcoming the resilient force of some bistable cells, i.e. those proximal to the passage areas of the second holding element, possibly until they are brought into the first stable position.

[0183] In the illustrated case in which the retention elements 240,245 are cables, a first cable forming part of the first retention element 240, or constituting it, is connected to a first side of an end support frame 40b of the extensible structure and to a first side of a tail support frame 65b of the extensible structure, for example after inserting it into the through holes 250 present in the support frames. A second cable forming part of the second retention element 245, or constituting it, is connected to a second side of the head support frame 40b of the extensible structure, for example after inserting it into the through holes present in the support frames. The second sides are substantially diametrically opposed to the first sides with respect to a central area or center of gravity of the respective support frames, for example in the illustrated embodiment, the first sides are each substantially a left vertical column of said support frames and the second sides are substantially each one is a vertical column on the right of said support frames (it is specified that right and left refer solely to figure 10). Subsequently the second side of the head support frame is pulled by acting on the second cable so as to fix the second cable to a second side of the tail support frame 65b of the extensible structure, in the case in which the cables of the first and second detention are of different length at the start. Alternatively, the cables of the first and second retaining element can initially have the same length and the second cable, after having been fixed to the second side of the head frame and having been inserted into the appropriate through holes 250 of the support frames, including the tail support frame, is pulled while holding the tail support frame still. As a consequence of this, the second side of the head support frame approaches the second side of the tail support frame, partially compressing (i.e. without bringing them into the first stable state) at least the bistable cells 100 proximal to the second cable. Once the desired curvature of the extensible structure has been reached, i.e. the maximum desired distance between the second sides of the head and tail frames, the second cable can be fixed, possibly also shortened first, to the second side of the tail support frame in order to prevent a distancing of the second sides compared to the distance reached.

[0184] It cannot be ruled out that in an alternative embodiment not illustrated, other flexible connecting bodies could be present instead of the cables, such as for example chains or ribbons, or that rigid rods could be present instead of the flexible connecting bodies. the extensible structure 15a, 15b can include one or more actuators (not shown) configured to act on the bistable cells by moving the first connection section 105 and the second connection section 110 apart from each other, for example by acting directly on the individual cells or by acting on the first support frame and second support frame by moving them apart. In particular, these actuators can be configured to generate a force such as to bring the cells from the first stable position to the unstable equilibrium position and from there provide a predetermined further force in the direction of the second stable position, sufficient to trigger the automatic transition from the position of unstable equilibrium at the second intrinsic stable position of bistable cells.

[0185] Such actuators could be in the form of shape memory materials, such as SMA aluminum alloys (Shape memory alloy), or linear actuators, for example telescopic.

[0186] Regardless of whether the cells are in groups or single, they may have a maximum size, when in the first stable position, measured perpendicular to the direction of extension A, which does not exceed, or does not protrude outward, in a direction perpendicular to the direction of extension A with respect to the external perimeter of the support frame (and possibly to the internal perimeter if present).

[0187] It should be noted that in this discussion, "monolithic" means a body obtained from the solidification of a single casting or extrusion or molding and from the possible processing of this solidification only by removing material.

[0188] It should be noted that in this discussion when an element is defined as "rigid", it means that it cannot be significantly deformed under the normal workloads to which it is subjected. In particular, unlike an element defined as "resilient", a rigid body does not carry out its function mainly on the basis of its own deformation.

[0189] It should be noted that in this discussion, when a connection is defined as "solvable" or "removable", it is meant that the elements that take part in this connection are not damaged and / or significantly plastically modified during their union and separation, of so that the connection can be reused at least a plurality of times.

[0190] The operation of the invention is as follows.

[0191] First of all, the assembly can start from joining the base bodies of the support frames to form at least a pair of support frames, subsequently the bistable cells are fixed to the support frames in the number necessary to provide the desired extension, in the sense of maximum distance between the support frames.

[0192] Once the extensible structure has been assembled, if it is not already in the retracted condition, with all the bistable cells in the first stable position, it can be brought into this configuration by compressing the bistable cells, in order to take up as little space as possible when moving the structure itself.

[0193] Once the structure has been installed, it can be brought into the extended configuration, for example by acting manually or with tools or with the structure's own actuators, if present.

[0194] The extensible structure in particular can be extended by pulling the support frames so as to bring all or even just some bistable cells into the second stable position.

[0195] Once the structure has been extended, we proceed with the installation of the retaining elements, in particular both the first retaining elements and the second if the structure must follow a curved shape.

[0196] Once the retaining elements have been installed, it is possible to proceed with the installation of the other fixing elements and the possible positioning of the pressurization bag. The pressurization bag, if present, can in turn be protected by a further internal lining, designed to prevent cuts or damage that could lead to an involuntary loss of pressure inside the module.

[0197] It is not excluded that the retaining elements may not be present and therefore the fixing elements are installed directly, and after these the external cladding and the internal cladding if these do not also have the function of fastening elements.

[0198] In the preferred embodiment illustrated by the drawings it is possible that, within each group, some cells are in the first stable, retracted, state, and some cells are in the second stable, expanded, state. In this preferred embodiment, all the groups connected in parallel within the same pair of support frames, where the entire structure is not curved but is partially, or entirely extended, along a straight stretch, have the same extension, i.e., have the same number of cells in the first or second stable state. It can be deduced that n bistable cells connected in series create n+1 stable states. Two groups of n cells in which m cells (m <n) are expanded and nm cells are retracted are in equivalent states of expansion (because they have the same extension), even if the expanded cells and the retracted cells do not have the same position in the respective groups. The entire structure, made up of series of groups of bistable cells, therefore creates a multistable construction, which has as many equivalent stable states as there are bistable cells that are counted moving along the +1 expansion direction.

[0199] Externally the entire structure can be wrapped in a protective sheet, capable of preventing the penetration of dust or other materials into the structure, especially if this must be covered with materials found on site, such as lunar regolith, to protect the structure from micrometeorites, harmful radiation and excessive temperature variations.

[0200] In the event that the structure must be placed in orbit, instead of using the regolith, an additional protective layer created for this purpose can be used.

[0201] When the structure needs to be repositioned, the internal and external coverings, as well as the retaining elements, are removed, and the extensible structure is then compressed into the retracted configuration, bringing all the bistable cells into the first stable position.

[0202] In the foregoing, the preferred embodiments have been described and variations of the present innovation have been suggested, but it is to be understood that experts in the art will be able to make modifications and changes without thereby departing from the relevant scope of protection, as defined by the claims, attached.

Claims

CLAIMS1. Extensible structure (15a, 15b) including:- a plurality of support frames (40a, 40b, 45a, 45b, 50a, 50b, 55a, 55b, 60a, 60b, 65b), of which at least a first support frame (40a, 40b), which is rigid, and a second support frame rigid (45a, 45b), which is rigid, each equipped with a first face (70a, 70b) and an opposite second face (75a, 75b),- a plurality of bistable cells (100) interposed between the first support frame and the second support frame, comprising at least a first cell (100) and a second cell (100), each equipped with:• a first connection section (105) and a second connection section (110), which connection sections are movable with respect to each other along an extension direction (A) of the cell itself, transversal to the first face (70a, 70b) and to the second face (75a, 75b) of the first support frame (40a, 40b) and of the second support frame (75a, 75b),• a first beam (150) and a second beam (160), rigid, each equipped with a first longitudinal end and a second longitudinal end, wherein the respective first longitudinal ends are hinged to each other at the first connection section (105) and the second longitudinal ends are rotatable with respect to the second connection section (110), and• a resilient element (170) which generates a force in the direction of mutual approach of the second longitudinal ends of said beams (150,160), said bistable cells (100) each being movable between a first stable position, in which the connecting sections (105,110) are located at a minimum mutual distance along the extension direction (A), and a second stable position, in which the connecting sections (105,110) are located at a maximum mutual distance along the extension direction (A), wherein in passing between the first stable position and the second stable position, each bistable cell (100) passes through an unstable equilibrium position, wherein each bistable cell (100) is characterized by an asymmetric behavior, requiring more energy in the passage from the second stable position to the first stable position than in the passage from the first stable position to the second stable position, wherein the first connection section (105) and the second connection section (110) are configured to connect the respective cell (100) indifferently to the first connection section (105) of another cell or to the second connection section (110) of another cell or to the first or to the second support frame, by means of a snap-fit connection removable even without the use of tools,in which said first and second cells (100) connect, independently to each other, the first and second support frames, and the variation of the position between the first stable position and the second stable position of said cells causes a variation, along said extension direction (A), of a mutual distance of the first support frame (40a, 40b) from the second support frame (45a, 45b).

2. Extensible structure (15a, 15b) according to claim 1, wherein the plurality of bistable cells (100) comprises a first group of cells, of which the first bistable cell is part, connected to each other in series at the respective connection sections (105,110) and aligned with each other along the respective extension directions (A), and a second group of cells, of which the second bistable cell is part, connected together in series in correspondence with the respective connection sections (105,110) and aligned with each other along the respective extension directions (A), and wherein the cells of the first group are connected to the first support frame (40a, 40b) and to the second support frame (45a, 45b) and the cells of the second group are connected to the first support frame (40a, 40b) and to the second support frame (45a, 45b), independently with respect to the cells of the first group.

3. Extensible structure (15b) according to any one of the previous claims, wherein the first support frame (40b) and the second support frame (45b) are shaped like annular bodies and the extensible structure (15b) is a tubular structure of containment.

4. Extensible structure (15b) according to any of the previous claims, includes a retaining element (240) connected to the first support frame (40b) and to the second support frame (45b) and fixed to them, which retaining element limits a maximum distance between said first support frame (40b) and second support frame (45b) along the extension direction (A).

5. Extensible structure (15b) according to the previous claim, wherein in addition to the retaining element (240) there is a second retaining element (245), which connects the first support frame (40b) and the second to each other support frame (45b) from sides thereof which are opposite to sides thereof connected by the first retaining element (240), and wherein the second retaining element (245) determines a maximum distance between the sides of the support frames that it connects, less than a maximum distance determined by the first retaining element between the sides of the supporting frame that it connects.

6. Extensible structure (15b) according to any of the previous claims, wherein the first support frame (40b) and the second support frame (45b) each comprise a plurality of base bodies (80b, 85b) fixed in such a way removable from each other, optionally via removable and / or quick release interlocking connections.

7. Extensible structure (15b) according to any one of claims 3 to 6, comprising a plurality of rigid plate-like covering elements (30), which can be removably connected to the first and second support frames (40b, 45b) and overall they create a tubular wall for the internal covering of the extensible tubular structure.

8. Extensible structure (15a, 15b) according to claim 1, wherein the bistable cell (100) is of the type based on the Von Mises truss principle.

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