Foldable prism structure with rotational symmetric motion

Abstract

The foldable prism structure comprises an upper bottom surface and a lower bottom surface, and the upper bottom surface and the lower bottom surface are both regular polygons with the number of edges larger than or equal to 3. Each edge of the upper bottom surface is rotatably connected with a folding and unfolding module to form a folding and unfolding unit, the folding and unfolding modules are the same in structure, each folding and unfolding module is sequentially composed of a first surface, a second surface and a third surface, and the first surface and the second surface are two congruent right triangle surfaces; the third face is a rectangular face, and any two adjacent edges of the third face are equal to the right-angle edges of the right triangle face. The first face and the second face are hinged through a rotating pair, and the second face and the third face are hinged through a rotating pair. Each edge of the lower bottom surface is rotatably connected with a folding and unfolding unit; every two adjacent folding and unfolding modules are mutually connected through a revolute pair formed by the edge, not forming the revolute pair with the upper bottom face, of the first face of one folding and unfolding module and the adjacent edge of the third face of the adjacent folding and unfolding module. And the plurality of folding and unfolding modules are rotationally and symmetrically distributed relative to the central axis of the foldable and unfolding prism structure in space.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of foldable prismatic structures, in particular to a foldable prismatic structure with a large fold-to-deploy ratio and rotational symmetry motion. BACKGROUND

[0002] Foldable structures are structures with controllable and variable geometry, which can realize the conversion between the compact folded state and the target deployed state. When such structures are in the folded state, they have a small volume for easy storage and transportation, or have high stiffness / self-locking characteristics for supporting functions, and when in the deployed state, they can meet the normal working requirements. Due to its good folding characteristics, foldable structures have been widely used in aerospace, biomedical, construction engineering and other fields. For example, satellite antennas are compressed by folding to adapt to the space limitations of rocket cargo bays, solar cell arrays rely on deployment mechanisms to achieve large-area energy collection, and foldable vascular stents are designed to be miniaturized to complete minimally invasive interventional therapy.

[0003] There are many types of existing foldable structures, which can be divided into one-dimensional rod-shaped foldable structures, two-dimensional planar foldable structures, and three-dimensional body-shaped foldable structures according to their target deployed state geometry. Among them, one-dimensional rod-shaped foldable structures mainly involve folding in a single direction, such as space stretching arms; two-dimensional planar foldable structures mainly involve folding of planes and curved surfaces, such as solar cell arrays and satellite antennas; three-dimensional body-shaped foldable structures mainly involve folding of spherical surfaces, polyhedrons, prisms, etc. Most of such foldable structures achieve folding and unfolding through non-rigid deformation, such as automobile airbags and flexible space capsules. Currently, some three-dimensional body-shaped foldable structures can achieve rigid folding, such as the patent "Foldable box structure with face symmetry motion" (Publication No: CN111776402A), the patent "Single-degree-of-freedom foldable box structure" (Publication No: CN109353634B), and the patent "Foldable box structure with rotational pair symmetry arrangement" (Publication No: CN111846510A) achieve rigid folding of the components of the prismatic structure by removing the upper base and designing folds on the side surfaces. However, there are relatively few applications of prismatic structures with supporting capabilities in the prismatic state and achieving rigid folding, and there are also deficiencies such as a small fold-to-deploy ratio. SUMMARY

[0004] The present application aims to overcome the deficiencies in the prior art, and provides a foldable prismatic structure with rotational symmetry, which has an unfolded state and a folded state: the unfolded state has a larger working space; the folded state forms a closed internal space, has good rigidity, and has a small volume for convenient storage and transportation. The structure is simple in composition, adjustable in geometric parameters, and can be mass-produced. Based on the above advantages, the present application has important significance and broad application prospects in the fields of storage, packaging, civil engineering, construction, aerospace, etc.

[0005] The present application aims to overcome the deficiencies in the prior art, and provides a foldable prismatic structure with rotational symmetry, which has an unfolded state and a folded state: the unfolded state has a larger working space; the folded state forms a closed internal space, has good rigidity, and has a small volume for convenient storage and transportation. The structure is simple in composition, adjustable in geometric parameters, and can be mass-produced. Based on the above advantages, the present application has important significance and broad application prospects in the fields of storage, packaging, civil engineering, construction, aerospace, etc.

[0006] A foldable prismatic structure with rotational symmetry, comprising an upper bottom surface and a lower bottom surface, both of which are regular polygons with a side number of 3 or more;

[0007] Each edge of the upper bottom surface is rotatably connected to a folding module to form a folding unit, and each folding module has the same structure and is sequentially composed of a first face, a second face and a third face. The first face and the second face are two congruent right-angled triangular faces, and the third face is a rectangular face with any two adjacent sides being equal to the right-angled sides of the right-angled triangular faces.

[0008] The first face and the second face are hinged through a first revolute pair, and the second face and the third face are hinged through a second revolute pair.

[0009] Each edge of the lower bottom surface is rotatably connected to a folding unit, and the adjacent edges of the upper bottom surface and the first face of each folding module are connected through an upper revolute pair, and the adjacent edges of the lower bottom surface and the third face of any folding module in the corresponding folding unit are connected through a lower revolute pair.

[0010] The adjacent folding modules are connected to each other through the rotation of the edge of the first face of one folding module that does not form a revolute pair with the upper bottom surface and the adjacent edge of the third face of the adjacent folding module.

[0011] Wherein, a plurality of folding modules are distributed in space with rotational symmetry about the central axis of the foldable prismatic structure, and the upper bottom surface and the lower bottom surface remain parallel in the fully unfolded and folded states, and form a foldable prismatic structure that can be reversibly converted between the unfolded and folded states.

[0012] Further, in the folding process, the geometric center of the upper bottom surface moves linearly along the central axis relative to the lower bottom surface during the unfolding to folding process, and a stable folded state is obtained when the distance between the geometric centers reaches the minimum; the compression resistance is maximum when fully folded, and a cavity is left in the middle for filling.

[0013] Further, the thickness of the out-of-plane direction of the first face, the second face and the third face is increased to form a thick plate panel, and the rotation pair connection relationship of each adjacent face is maintained to realize the folding of the thick plate prism structure.

[0014] Further, the number of polygonal sides of the upper base and the lower base is changed to change the number of folding and unfolding modules, so as to adjust the motion characteristics, folding and unfolding ratio and working space of the foldable prism structure.

[0015] Further, the rotation pair is any one of a hinge, a hinge or a bearing.

[0016] Further, the folding and unfolding process of rigid folding or non-rigid folding is realized by setting a fold line on the first face, the second face and the third face or using a bendable connecting piece.

[0017] Further, the number of sides of the upper base / lower base in the unfolded state is 3, 4 or 6.

[0018] Preferably, the present application also provides a foldable prism combined structure, comprising at least two foldable prism structures, and each foldable prism structure is connected to each other through the folding and unfolding units of each other.

[0019] Preferably, the present application also provides a folding and unfolding method of a foldable prism structure, comprising:

[0020] The foldable prism structure is provided; each foldable prism structure is driven to rotate synchronously around the first rotation pair and the second rotation pair, so that the upper base approaches or moves away from the lower base along the central axis direction, and the upper base and the lower base are parallel in the completely unfolded and folded states, so that the foldable prism structure is switched between the unfolded and folded states.

[0021] Compared with the prior art, the technical scheme of the present application has the beneficial effects that:

[0022] 1. The foldable prism structure comprises a plurality of folding and unfolding modules composed of two congruent right-angled triangles and a rectangle, a plurality of folding and unfolding modules are sequentially hinged on the upper base through the rotation pairs to form folding and unfolding units, and a plurality of folding and unfolding units are sequentially hinged on the lower base through the rotation pairs; the geometric constraint that the right-angled side is equal to the adjacent side of the rectangle makes the folding and unfolding modules form a rotationally symmetric cooperative motion under the driving of the rotation pairs, the top / bottom boundary is controlled, and a stable prism shape and a predictable folding and unfolding trajectory are formed; the foldable prism structure protected by the present application has simple overall structure, strong panel versatility, and is convenient for processing and mass production; the folding and unfolding process is controllable and can be completely folded, and the folding and unfolding ratio is large. The problems of the traditional three-dimensional foldable structure, such as the dependence on flexible unfolding or the need to remove the upper base and set a fold line on the side to realize rigid folding, the difficulty in considering both the supporting ability of the prism state and the folding state, and the limitation of the folding and unfolding ratio, are solved.

[0023] 2. The upper and lower bottom surfaces are regular polygons and always remain parallel in the fully unfolded and folded states; the foldable and unfoldable modules are distributed in rotational symmetry around the central axis. The parallel boundary constraint combined with the rotational symmetry distribution makes the geometric center of the upper and lower bottom surfaces move linearly along the central axis, ensuring that the prism does not twist during the entire stroke; and when the center distance is the smallest, a stable position is formed. The working space in the folded state is large; after folding, it is regular, stacked in a three-layer plate-thick shape (see Figures 1-3 ), small in volume, easy to store and transport.

[0024] 3. The number of polygon sides is changed to change the number and geometric parameters of the foldable and unfoldable modules. The number of sides of the upper and lower bottom surfaces directly determines the number of circumferential foldable and unfoldable modules and the distribution of the revolute pair positions, thereby changing the kinematic and mechanical properties. Various specifications such as three edges, four edges, and six edges can be obtained, and the motion characteristics and foldable and unfoldable ratios can be designed as needed; solving the problem of large differences in requirements for foldable and unfoldable ratios, working space, and shape dimensions in different applications.

[0025] 4. The thickness can be increased in the out-of-plane direction while maintaining the connection of the revolute pair; the thickness is raised in cooperation with the appropriate revolute pair gap and axis arrangement, which can achieve the foldable and unfoldable of thick plates without interference. It can significantly improve the structural stiffness and strength, and be expanded to load-bearing or impact-resistant scenarios; still maintaining the foldable and unfoldable characteristics; solving the problem of insufficient structural stiffness and limited load-carrying capacity of thin plates.

[0026] 5. Variable stiffness characteristics and fillable cavities; the stress path gradually shortens during the folding process and tends to be close to face-to-face, the increase in contact area increases the overall equivalent stiffness; the compression resistance reaches the maximum when fully folded, and an internal fillable cavity is formed. Get a variable stiffness response of soft when unfolded and hard when folded, which can be used for vibration absorption and energy absorption, packaging protection, etc.; the folding cavity can be filled with materials as needed; solving the problem of meeting the requirements of softness and unfoldability in the unfolded state, and having support / compression resistance after folding.

[0027] 6. The upper and lower bottom surfaces between the multi-prisms are connected by foldable and unfoldable units; the regular polygon is used as the connection primitive to arrange in rotation, realizing a regular array or a ring array; after adding a central polygon to seal, a continuous mechanical boundary and synchronous foldable and unfoldable are obtained; realizing a multi-unit space self-assembly type deployable system, which can be used for space dwellings, extraterrestrial housing groups, or large-size deployable components. Solving the problem of limited single volume, difficulty in forming large-scale space and complex arrangement, etc.

[0028] 7. The connection is diversified, and the revolute pair can be a hinge, a hinge, or a bearing; the functionally equivalent revolute pair is replaced to maintain the kinematics unchanged while optimizing the process and service life; improving adaptability and manufacturability, facilitating mass production; solving the problem that different working conditions have different requirements for friction, durability, and assembly process. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1-1A planar unfolded schematic view of the foldable module involved in the present application, Figure 1-2 and Figure 1-3 are respectively a structural schematic view of the foldable module at a certain time during the folding process and a schematic view of the folded state structure of the foldable module.

[0030] Figure 2-1 is a structural schematic view of the unfolded state of the foldable unit in the form of a foldable triangular prism structure of Example 1, Figure 2-2 and Figure 2-3 are respectively a schematic view of a certain state of each foldable module in the foldable triangular prism structure of Example 1 during the folding process and a schematic view after folding. Figure 2-4 and Figure 2-5 are respectively a structural schematic view of the foldable unit T2 in the form of a foldable triangular prism structure and a structural schematic view of one edge of the lower base BI1 in the unfolded and folded states.

[0031] Figure 3-1 is a structural schematic view of the unfolded state of the foldable prism structure of Example 1 (if the creases shown by the dashed lines exist, the folding process is rigid folding; if the creases shown by the dashed lines do not exist, the folding process is non-rigid folding), Figure 3-2 is a schematic view of the folded state of the foldable prism structure of Example 1, Figure 3-3 is a schematic view of the overall folded state of the foldable prism structure of Example 1 after arranging a plurality of foldable prism structures.

[0032] Figure 4-1 is a structural schematic view of the unfolded state of the foldable unit in the form of a foldable quadrangular prism structure of Example 2, Figure 4-2 and Figure 4-3 are respectively a schematic view of a certain state of each foldable module in the foldable quadrangular prism structure of Example 2 during the folding process and a schematic view after folding. Figure 4-4 and Figure 4-5 are respectively a structural schematic view of the foldable unit U2 in the form of a foldable quadrangular prism structure and a structural schematic view of one edge of the lower base CI1 in the unfolded and folded states.

[0033] Figure 5-1 is a structural schematic view of the unfolded state of the foldable prism structure of Example 2 (if the creases shown by the dashed lines exist, the folding process is rigid folding; if the creases shown by the dashed lines do not exist, the folding process is non-rigid folding), Figure 5-2 is a schematic view of the folded state of the foldable prism structure of Example 2, Figure 5-3 is a schematic view of the overall folded state of the foldable prism structure of Example 2 after arranging a plurality of foldable prism structures.

[0034] Figure 6-1 is a structural schematic view of the unfolded state of the foldable unit in the form of a foldable hexagonal prism structure of Example 3, Figure 6-2 and Figure 6-3Respectively, the schematic diagram of each folding module in the folding process and the schematic diagram of the folded state of the folding module in the folding hexagonal prism structure of example three. Figure 6-4 and Figure 6-5 Respectively, the schematic diagram of the structure of the folding unit V2 and one edge of the lower bottom surface DI1 being hinged and being in the unfolded and folded state.

[0035] Figure 7-1 The schematic diagram of the unfolded state of the folding prism structure of example three (the creases shown by the dotted lines in the figure exist, and the folding process is rigid folding; if the creases shown by the dotted lines do not exist, the folding process is non-rigid folding), Figure 7-2 The schematic diagram of the folded state of the folding prism structure of example three, Figure 7-3 The schematic diagram of the overall folded state of the folding prism structure of example three. DETAILED DESCRIPTION

[0036] The application will be described in further detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0037] Figure 1-1 is the unfolding pattern of the folding module of the folding prism structure in the application, which is composed of two congruent right triangles with an acute angle and a rectangle with any two adjacent sides equal to the lengths of the two right sides of the above right triangle. The first face and the second face of the two congruent triangles are A1 and A2 respectively; the rectangular face is A3; the first face A1 is adjacent to the second face A2 and is connected to each other through the first revolute pair L1, and the second face A2 is adjacent to the third face A3 and is connected to each other through the second revolute pair L2. Among them, A1 is folded outward around L1 to form a convex shape, A3 is folded outward around L2 to form a convex shape, and the folded shape of the folding module is shown as Figure 1-2 , and the folding module is formed to form the folding prism structure. Continue to fold until A1 and A2 are attached, and A2 and A3 are attached, and the shape of the folding module is shown as Figure 1-3 . Among them represents an acute angle in the right triangle in the folding module.

[0038] Example one:

[0039] This embodiment is based on the fact that the upper bottom surface B1 and the three folding modules I1, I2 and I3 together constitute a folding unit T1 in the form of a triangular prism structure, Figure 2-1 is the completely unfolded state of the folding unit T1, the upper bottom surface B1 is a regular triangle, and the structural parameters of the three folding modules I1, I2 and I3 are the same, as described in the folding module Figure 1-1 . At this time The upper bottom surface B1 is adjacent to the first surface of the folding and unfolding module I1 and is hingedly connected to each other through the upper rotating joint M1. In clockwise order, the upper bottom surface B1 is adjacent to the first surface of the folding and unfolding module I2 and is hingedly connected to each other through the upper rotating joint M2, and the upper bottom surface B1 is adjacent to the first surface of the folding and unfolding module I3 and is hingedly connected to each other through the upper rotating joint M3, thereby forming the folding and unfolding unit T1 in the form of a foldable triangular prism structure.

[0040] According to the arrangement and connection mode of the upper bottom surface and the folding and unfolding module, Figures 2-2 to 2-3 for the folding process of the folding and unfolding unit T1. Figure 2-2 for the intermediate state of the folding process of the folding and unfolding unit T1 in the form of a foldable triangular prism structure, Figure 2-3 for its completely folded state.

[0041] Figure 2-4 for a structural schematic view in which one folding and unfolding unit T2 is hingedly connected to one edge of the lower bottom surface BI1 through the lower rotating joint MI2 and is in an unfolded state, Figure 2-5 for a structural schematic view in which the folding and unfolding unit T2 is hingedly connected to one edge of the lower bottom surface BI1 through the lower rotating joint MI2 and is in a folded state, wherein the upper bottom surface B2 is connected to the folding and unfolding modules I4-I6 through the upper rotating joints M4-M6; the other lower rotating joints of the lower bottom surface BI1 are MI1, MI3, MI4, MI5 and MI6.

[0042] As Figure 3-1 shown, the above-mentioned foldable triangular prism structure can be combined by six foldable triangular prism structures through the lower bottom surface BI1 in the form of a regular hexagon, so as to construct a foldable prism structure with larger arrangement capacity. Among them, the folding and unfolding units T1, T2, T3, T4, T5 and T6 in the form of a foldable triangular prism structure are sequentially connected to the edges of the lower bottom surface B11, forming six new rotating joints. In the completely unfolded and folded states of the above-mentioned foldable prism structure, the upper bottom surfaces B1, B2, B3, B4, B5 and B6 are parallel to the lower bottom surface BI1, and each folding and unfolding module moves according to the mode in the description. According to Figure 1-1 the unfolded state of the combination mode of the foldable triangular prism structure model shown in Figure 3-1 . Figure 3-2 for the completely folded state of the foldable triangular prism combination structure. Figure 3-3 for the completely folded state of the combination structure of four Figure 3-2 as shown; a total of 24 folding and unfolding units T1-T24 are involved.

[0043] Example Two:

[0044] This embodiment is based on the upper bottom surface C1 and four folding and unfolding modules II1-II4 jointly forming a folding and unfolding unit U1 in the form of a quadrangular prism structure, Figure 4-1For the fully unfolded state of the foldable unit U1, the upper base C1 is a square, and the four foldable modules II1, II2, II3, and II4 have the same structural parameters. Referring to Figure 1-1 the foldable module, at this time . The upper base C1 is adjacent to the first face of the foldable module II1 and is hingedly connected through the upper revolute pair N1. In clockwise order, the upper base C1 is adjacent to the first face of the foldable module II2 and is hingedly connected through the upper revolute pair N2, the upper base C1 is adjacent to the first face of the foldable module II3 and is hingedly connected through the upper revolute pair N3, and the upper base C1 is adjacent to the first face of the foldable module II4 and is hingedly connected through the upper revolute pair N4, thereby forming a foldable unit U1 in the form of a foldable quadrangular prism structure.

[0045] According to the above arrangement and connection mode of the upper base and the foldable module, Figures 4-2 to 4-3 is the folding process of the foldable unit U1. Figure 4-2 is an intermediate state of the foldable unit U1 in the form of a foldable quadrangular prism structure during folding, Figure 4-3 is its fully folded state.

[0046] Figure 4-4 is a structural schematic diagram of one of the foldable units U2 and one edge of the lower base CI1 being hingedly connected through the lower revolute pair NI3 and being in an unfolded state, Figure 4-5 is a structural schematic diagram of the foldable unit U2 and one edge of the lower base CI1 being hingedly connected through the lower revolute pair NI3 and being in a folded state. In the figure, the upper base C2 is connected to the foldable modules II5-II8 through the upper revolute pairs N5-N8, respectively; and the other lower revolute pairs of the lower base CI1 are NI1, NI2, and NI4.

[0047] As Figure 5-1 shown, the above foldable quadrangular prism structure can be combined into four foldable quadrangular prism structures through the lower base CI1 of the intermediate square to construct a foldable prism structure with stronger arrangement capability. Among them, the foldable units U1, U2, U3, and U4 in the form of a foldable quadrangular prism structure are sequentially connected to the edges of the lower base CI1, forming four new revolute pairs. In the fully unfolded and folded states of the above foldable prism structure, the upper bases C1, C2, C3, and C4 are parallel to the lower base CI1, and each foldable module moves according to the Figure 1-1 description. According to Figure 5-1 the unfolded state of the combination mode of the foldable quadrangular prism structure model. Figure 5-2 is the fully folded state of the foldable quadrangular prism combination structure. Figure 5-3 is the fully folded state of the four combination structures as Figure 5-2 shown after further arrangement, involving foldable units U1-U16.

[0048] Example Three:

[0049] In this embodiment, the upper bottom surface D1 and six unfolding modules III1 to III6 together form an unfolding unit V1 with a hexagonal prism structure. Figure 4-1 This represents the fully unfolded state of folding unit V1. The upper base D1 is a regular hexagon. The six folding modules III1~III6 have the same structural parameters. (Refer to...) Figure 1-1 The folding module is now in operation. The upper bottom surface D1 is adjacent to the first surface of the unfolding module III1 and is hinged to each other through the upper revolute joint O1. In clockwise order, the upper bottom surface D1 is adjacent to the first surface of the unfolding module III2 and is hinged to each other through the upper revolute joint O2; the upper bottom surface D1 is adjacent to the first surface of the unfolding module III3 and is hinged to each other through the upper revolute joint O3; the upper bottom surface D1 is adjacent to the first surface of the unfolding module III4 and is hinged to each other through the upper revolute joint O4; the upper bottom surface D1 is adjacent to the first surface of the unfolding module III5 and is hinged to each other through the upper revolute joint O5; and the upper bottom surface D1 is adjacent to the first surface of the unfolding module III6 and is hinged to each other through the upper revolute joint O6. This constitutes the unfolding unit V1, which has a unfoldable hexagonal prism structure, according to the above arrangement and connection of the upper bottom surfaces and unfolding modules. Figures 6-2 to 6-3 This describes the folding process of the unfolding unit V1. Figure 6-2 This is an intermediate state during the folding process of the unfolding unit V1, which has a unfoldable hexagonal prism structure. Figure 6-3 It is in its fully folded state.

[0050] Figure 6-4 This is a schematic diagram of a structure in which one of the unfolding units V2 is hinged to one side of the lower bottom surface DI1 through the lower revolute joint OI2 and is in the unfolded state. Figure 6-5 The diagram shows the structure of the unfolding unit V2 and the lower bottom surface DI1, which are hinged to each other through the lower rotating joint OI2 and are in a folded state. In the diagram, the upper bottom surface D2 is connected to the unfolding module III7 to III12 through the upper rotating joints O7 to O12 respectively; the other lower rotating joints of the lower bottom surface DI1 are OI1 and OI3.

[0051] like Figure 7-1 As shown, the aforementioned foldable hexagonal prism structure can be constructed by combining three foldable hexagonal prism structural modules through the lower base DI1 of the central equilateral triangle, thereby creating a foldable prism structure with stronger arrangement capabilities. Specifically, the foldable hexagonal prism units V1, V2, and V3 are sequentially connected to the edges of the lower base DI1, forming three new revolute joints. In both the fully unfolded and folded states, the upper bases D1, D2, and D3 of the aforementioned foldable prism structure remain parallel to the lower base DI1, and each foldable module is arranged according to... Figure 1-1 The movement is as described in the instructions. Follow the... Figure 7-1 The unfolded state of the foldable hexagonal prism structure model shown.Figure 7-2 is the fully folded state of the combined structure of the foldable hexagonal prism. Figure 7-3 is the fully folded state of the combined structure of the four foldable prisms, and the involved foldable units are V1-V4. Figure 7-2 is the fully folded state of the combined structure of the four foldable prisms, and the involved foldable units are V1-V4.

[0052] It can be seen that the foldable prism structure described above can achieve the folding and unfolding effect required by the present application as long as the above constraints and the connection mode of the revolute pairs are met. The size of each face can be changed according to the actual application requirements. The foldable prism structure of the present application has a large folding and unfolding ratio, can be unfolded and completely folded flat, is convenient for storage and transportation, is simple, and is convenient for processing, manufacturing and mass production, and has important significance and broad application prospects in the fields of storage, packaging, civil engineering, construction, aerospace, etc.

[0053] The present application is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solutions of the present application, and the specific embodiments described above are merely illustrative and not restrictive. Without departing from the purpose of the present application and the scope protected by the claims, those skilled in the art can make many forms of specific changes under the inspiration of the present application, and these all belong to the protection scope of the present application.

Claims

1. A foldable prism structure with rotational symmetry, characterized in that, It includes the top and bottom faces, both of which are regular polygons with ≥3 sides; Each edge of the top surface can be rotatably connected to a folding module to form a folding unit. Each folding module has the same structure. Each folding module is composed of a first surface, a second surface and a third surface in sequence. The first surface and the second surface are two congruent right-angled triangles. The third surface is a rectangular surface and any two adjacent sides of it are equal to the right-angled sides of the right-angled triangles. The first surface and the second surface are hinged together by a first revolute joint, and the second surface and the third surface are hinged together by a second revolute joint. Each edge of the bottom surface can be rotatably connected to one of the aforementioned folding and unfolding units. The upper bottom surface is connected to the adjacent edge of the first surface of each folding and unfolding module through an upper revolute joint. The lower bottom surface is connected to the adjacent edge of the third surface of any folding and unfolding module in the corresponding folding and unfolding unit through a lower revolute joint. Adjacent folding modules are connected by a rotating joint formed between the side of the first surface of one folding module that does not form a rotating joint with the upper bottom surface and the adjacent side of the third surface of the adjacent folding module. Among them, several of the folding modules are distributed in space in a rotationally symmetrical manner about the central axis of the foldable prism structure. The upper and lower bottom surfaces remain parallel in the fully unfolded and folded states, forming a foldable prism structure that can be reversibly converted between the unfolded and folded states.

2. The foldable prism structure with rotational symmetry motion according to claim 1, characterized in that, During the unfolding process, it exhibits variable stiffness characteristics. The geometric center of the upper bottom surface moves in a straight line relative to the lower bottom surface along the central axis, and a stable folded state is obtained when the distance between the two geometric centers reaches its minimum. The compressive strength is maximized when fully folded, and a cavity is left in the middle for filling.

3. The foldable prism structure with rotational symmetry motion according to claim 1, characterized in that, Thickness is added to the out-of-plane direction of the first, second, and third surfaces to form a thick plate panel, while maintaining the rotational joint connection relationship of each adjacent surface, thereby realizing the folding of the thick plate prism structure.

4. The foldable prism structure with rotational symmetry motion according to claim 1, characterized in that, The number of folding modules can be changed by altering the number of sides of the regular polygons on the upper and lower surfaces, thereby adjusting the motion characteristics, folding ratio, and workspace of the foldable prism structure.

5. The foldable prism structure with rotational symmetry motion according to claim 1, characterized in that, The revolute joint is any one of a hinge, a hinge assembly, or a bearing.

6. The foldable prism structure with rotational symmetry motion according to claim 1, characterized in that, The folding and unfolding process can be achieved by setting creases on the first, second, and third surfaces or by using flexible connectors to achieve rigid or non-rigid folding.

7. The foldable prism structure with rotational symmetry motion according to claim 1, characterized in that, When unfolded, the number of sides of its top / bottom face is 3, 4, or 6.

8. A foldable prism combination structure, characterized in that, It includes at least two foldable prism structures as described in any one of claims 1 to 7, wherein the foldable prism structures are interconnected by each other through folding units.

9. A method for unfolding a foldable prism structure, characterized in that, include: Provides a foldable prism structure as described in any one of claims 1 to 7; Each foldable prism structure is driven to rotate synchronously around its first and second revolute joints, so that the upper bottom surface approaches or moves away from the lower bottom surface along the central axis. In both fully unfolded and folded states, the upper bottom surface and the lower bottom surface remain parallel, thus enabling the foldable prism structure to switch between unfolded and folded states.

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