A scissor-type variable Poisson's ratio folding and unfolding mechanism

Abstract

The present invention discloses a scissor-type variable Poisson's ratio folding and unfolding mechanism, which comprises a regular 2n-sided polygon structure formed by connecting a plurality of basic units to each other, where n≥2. The mechanism includes five types of rods, namely the first B rod, the second B rod, the third B rod, the C rod, and the D rod, with their lengths being k1, k2, k3, k4, and k5 respectively, and k1 = k2, 2k1 > k4. Each basic unit includes a first Z-shaped structure and a second Z-shaped structure. In each Z-shaped structure, the upper and lower ends of the C rod arranged obliquely are respectively hinged to two D rods arranged horizontally. The C rods of the two Z-shaped structures are cross-arranged and hinged to each other at the middle position. This mechanism can achieve circular expansion and expansion in the column direction through the first connecting piece and the second connecting piece. It is easy to be modularized, has the effect of variable Poisson's ratio, large space utilization rate, and the basic unit and the expansion unit have only one degree of freedom, enabling single-drive input and facilitating expansion.

Description

Technical Field

[0001] The present invention relates to a folding and unfolding mechanism, and particularly to a scissor-type variable Poisson's ratio folding and unfolding mechanism. Background Art

[0002] The deployable mechanism is integrated by prefabricated units and can be converted between an initial compact configuration and a deployed configuration in the working state. It generally has two states: a fully contracted state and a fully deployed state. The folding and unfolding mechanism is widely used in occasions with strict geometric restrictions on the executing member due to its small geometric envelope in the retracted state. Common examples in life include folding umbrellas, folding tables and chairs, space operating arms, solar wings, folding satellite antennas, etc. in aerospace technology.

[0003] The scissor mechanism has attracted much attention due to its simple structure, good reliability, and convenient assembly. Since PINERO applied it to mobile buildings, the scissor mechanism has been applied in various forms in fields such as life and aerospace, such as a deployable robotic arm composed of scissor units as basic units, and an annular deployable mechanism composed of three different scissor units.

[0004] Poisson's ratio is used to describe the longitudinal deformation phenomenon that occurs simultaneously with the lateral deformation of a material. Poisson's ratio is often applied to materials. When introduced into a mechanism, in a common traditional mechanism under a uniaxial tensile load, a state of inward contraction occurs perpendicular to the direction of the applied force, and such a mechanism is called a positive Poisson's ratio mechanism. A negative Poisson's ratio mechanism is one in which, under a uniaxial tensile load, an outward expansion phenomenon occurs perpendicular to the direction of the applied force. The biggest difference between a negative Poisson's ratio mechanism and a positive Poisson's ratio mechanism lies in this, that is, when subjected to a tensile load, the direction of the lateral displacement is opposite. Summary of the Invention

[0005] An object of the present invention is to overcome the drawbacks of the existing technology and provide a scissor-type variable Poisson's ratio folding and unfolding mechanism that has only one degree of freedom, can achieve single-drive input, and thus can ensure the synchronous unfolding of the mechanism after module expansion.

[0006] To this end, the technical solution of the present invention is as follows:

[0007] A scissor-type variable Poisson's ratio folding and unfolding mechanism of the present invention includes a regular 2n-sided structure formed by connecting a plurality of basic units to each other, where \(n\geq2\). Each basic unit includes a first Z-shaped structure and a second Z-shaped structure. The upper and lower ends of the C rod arranged obliquely in each Z-shaped structure are respectively hinged to two D rods arranged horizontally. The C rods of the two Z-shaped structures are cross-arranged at the middle position and hinged to each other at the cross position. The two upper D rods located above the two Z-shaped structures are coaxially arranged, and the two lower D rods located below the two Z-shaped structures are coaxially arranged. The outer ends of the lower D rods of the first Z-shaped structure and the outer ends of the D rods of the second Z-shaped structure, as well as the outer ends of the upper D rods of the first Z-shaped structure and the outer ends of the lower D rods of the second Z-shaped structure, are respectively connected by a parallelogram link mechanism. Each parallelogram link mechanism includes two first B rods, two second B rods, and one third B rod. The two first B rods and the two second B rods have the same length. Among them, the upper ends of the two first B rods arranged horizontally and spaced apart left and right are respectively hinged to the outer ends of the upper D rods of the first Z-shaped structure or the second Z-shaped structure and the rod segments of the upper D rods located inside the outer ends to form a first hinge point and a second hinge point. The lower ends of the two second B rods arranged horizontally and spaced apart left and right are respectively hinged to the outer ends of the lower D rods of the first Z-shaped structure or the second Z-shaped structure and the rod segments of the lower D rods located inside the outer ends to form a third hinge point and a fourth hinge point. The inner end of the third B rod arranged horizontally is jointly hinged to the lower end of the first B rod located inside and the upper end of the second B rod located inside to form a fifth hinge point, and the outer end of the third B rod is jointly hinged to the lower end of the first B rod located outside and the upper end of the second B rod located outside to form a sixth hinge point. The first parallelogram structure of the parallelogram link mechanism is formed by using the first hinge point, the second hinge point, the fifth hinge point, and the sixth hinge point as the four vertices of the quadrilateral. The second parallelogram structure of the parallelogram link mechanism is formed by using the third hinge point, the fourth hinge point, the fifth hinge point, and the sixth hinge point as the four vertices of the quadrilateral;

[0008] The ends of the two upper D rods located at the corners of the regular 2n-sided structure and the ends of the two lower D rods between two adjacent basic units on the left and right are respectively connected by a first connecting piece. Among them, the two sides of the upper first connecting piece are respectively hinged to the two first hinge points at the corner positions of the two basic units, and the two sides of the lower first connecting piece are respectively hinged to the two third hinge points at the corner positions of the two basic units. The first connecting piece is V-shaped, and the angle of the V-shaped included angle is the same as the angle of the interior angle of the regular 2n-sided structure;

[0009] Let the length of the first B rod be k1 , the length of the second B member is k 2 , the length of the third B member is k 3 , the length of the C member is k 4 , where k i > 0, i = 1, 2, 3, 4, and k 1 = k 2 , 2k 1 > k 4 .

[0010] The beneficial effects of the present invention are as follows:

[0011] 1. Compared with the traditional folding and unfolding mechanism, the scissor-type variable Poisson's ratio folding and unfolding mechanism proposed in this application has a negative Poisson's ratio and can also achieve the conversion between positive and negative Poisson's ratios, making the space occupied during contraction very small and the space very large during unfolding, thereby improving the space utilization rate; this mechanism has only one degree of freedom and can achieve single-drive input, thus ensuring the synchronous unfolding of the mechanism after module expansion. It has the advantages of simple structure, high load-bearing capacity, flexible operation, high space utilization rate, large movement space, and easy modular manufacturing.

[0012] 2. Compared with the traditional space folding and unfolding mechanism, the scissor-type variable Poisson's ratio folding and unfolding mechanism can achieve single-degree-of-freedom transmission, and the motion control is simple and reliable;

[0013] 3. Compared with the traditional space folding and unfolding mechanism, the scissor-type variable Poisson's ratio folding and unfolding mechanism can increase the area after unfolding by increasing the number of basic units, and the expansion method is simple, fast, and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of the scissor-type variable Poisson's ratio folding and unfolding mechanism provided by this application;

[0015] Figure 2 is a schematic diagram of the 2×2 expansion structure;

[0016] Figure 3 is a schematic diagram of the structure when compressed to the lowest in the negative Poisson's ratio stage;

[0017] Figure 4 is a schematic diagram of the structure during the conversion between positive and negative Poisson's ratios;

[0018] Figure 5 is a schematic diagram of the structure when compressed to the lowest in the positive Poisson's ratio stage;

[0019] Figure 6 is a schematic diagram of the single-layer expansion structure;

[0020] Figure 7 is a schematic diagram of the double-layer expansion structure.

[0021] Figure 8Schematic diagram of a double-layer structure with an extended positive Poisson's ratio

[0022] Figure 9 Schematic diagram of an n-layer extended structure; Specific implementation manner

[0023] The technical solution of the invention will be described in detail below in conjunction with the drawings and specific implementation manners:

[0024] A scissor-type variable Poisson's ratio folding and unfolding mechanism of the present invention as shown in the drawings includes a regular 2n-sided structure formed by connecting multiple basic units to each other, where n≥2. As Figure 1 shown, each basic unit includes a first Z-shaped structure and a second Z-shaped structure. The upper and lower ends of the C rod arranged obliquely in each Z-shaped structure are respectively hinged to two D rods arranged horizontally. The C rods of the two Z-shaped structures are cross-arranged at the middle position and hinged to each other at the cross position. The two upper D rods in the two Z-shaped structures are coaxially arranged, and the two lower D rods in the two Z-shaped structures are coaxially arranged. The outer ends of the lower D rod of the first Z-shaped structure and the D rod of the second Z-shaped structure, and the outer ends of the upper D rod of the first Z-shaped structure and the lower D rod of the second Z-shaped structure are respectively connected by a parallelogram link mechanism. Each parallelogram link mechanism includes two first B rods, two second B rods, and one third B rod. The two first B rods and the two second B rods have the same length. Among them, the two first B rods arranged horizontally and spaced apart are respectively hinged to the outer ends of the upper D rods in the first Z-shaped structure or the second Z-shaped structure and the rod segments of the upper D rods located inside the outer ends to form a first hinge point and a second hinge point. The two second B rods arranged horizontally and spaced apart are respectively hinged to the outer ends of the lower D rods in the first Z-shaped structure or the second Z-shaped structure and the rod segments of the lower D rods located inside the outer ends to form a third hinge point and a fourth hinge point. The inner end of the third B rod arranged horizontally is jointly hinged to the lower end of the first B rod located inside and the upper end of the second B rod located inside to form a fifth hinge point, and the outer end of the third B rod is jointly hinged to the lower end of the first B rod located outside and the upper end of the second B rod located outside to form a sixth hinge point. A first parallelogram structure of the parallelogram link mechanism is formed by the first hinge point, the second hinge point, the fifth hinge point, and the sixth hinge point as the four vertices of the quadrilateral. A second parallelogram structure of the parallelogram link mechanism is formed by the third hinge point, the fourth hinge point, the fifth hinge point, and the sixth hinge point as the four vertices of the quadrilateral.

[0025] The ends of two upper D bars located at the corners of the regular 2n-sided structure in two adjacent basic units on the left and right are respectively connected by a first connecting member, and the ends of two lower D bars are respectively connected by a first connecting member. The two sides of the upper first connecting member are respectively hinged to two first hinge points at the corner positions of the two basic units, and the two sides of the lower first connecting member are respectively hinged to two third hinge points at the corner positions of the two basic units. The first connecting member is V-shaped, and the angle of the V-shaped angle is the same as the angle of the interior angle of the regular 2n-sided structure.

[0026] Let the length of the first B bar be k 1 , and the length of the second B bar be k 2 , and the length of the third B bar be k 3 , and the length of the C bar be k 4 , where k i >0, i = 1, 2, 3, 4, and k 1 =k 2 , 2k 1 >k 4 .

[0027] Next, combined with the Figure 1 of the present invention, the basic unit of the present invention will be described in detail:

[0028] The basic unit includes five types of bars according to length, which are respectively marked as including the first B bar, the second B bar, the third B bar, the C bar, and the D bar.

[0029] Among them: there are four first B bars, which are respectively marked as CE, DF, C 1 E 1 , D 1 F 1 ;

[0030] There are four second B bars, which are respectively marked as AC, BD, A 1 C 1 , B 1 D 1 ;

[0031] There are two third B bars, which are respectively marked as CD, C 1 D 1 ;

[0032] There are two C bars, which are respectively marked as GH 1 , G 1 H;

[0033] There are four D bars, which are respectively marked as AH, EG, A 1 H 1 , E 1 G 1 ;

[0034] Assume that the length of the first B member is k 1 , and the length of the second B member is k 2 , and the length of the third B member is k 3 , and the length of the C member is k 4 . Where k i > 0 (i = 1, 2, 3, 4). And k 1 = k 2 , 2k 1 > k 4 , AB = EF = A 1 B 1 = E 1 F 1 = k 3 .

[0035] As the second embodiment of the present invention, there are at least two regular 2n-sided polygon structures, and at least two regular 2n-sided polygon structures are stacked and connected to each other up and down to form a regular 2n-sided polygon integrated multi-layer structure. For each upper basic unit arranged in an up-and-down alignment and stacked in the regular 2n-sided polygon integrated multi-layer structure, the two lower D members respectively support on the two upper D members of the lower basic unit arranged in alignment, and the third hinge points and the first hinge points arranged in a left-right and up-down corresponding manner in the two basic units at the stacking position are respectively jointly hinged to the second connecting member. Between the adjacent side outer ends of the two upper D members located at the corner of the regular 2n-sided polygon structure in the left and right adjacent basic units in the uppermost regular 2n-sided polygon structure of the regular 2n-sided polygon integrated multi-layer structure, they are connected by the upper first connecting member, and both sides of the upper first connecting member are respectively hinged to the two first hinge points of the two upper D members located at the corner of the regular 2n-sided polygon structure. And between the adjacent side outer ends of the two lower D members located at the corner of the regular 2n-sided polygon structure in the left and right adjacent basic units in the lowermost 2n-sided polygon structure of the regular 2n-sided polygon integrated multi-layer structure, they are connected by the lower first connecting member, and both sides of the lower first connecting member are respectively hinged to the two third hinge points of the two lower D members located at the corner of the regular 2n-sided polygon structure. The first connecting member is V-shaped, and the angle of the V-shaped angle is consistent with the angle of the interior angle of the regular 2n-sided polygon structure.

[0036] The present invention will be further described in detail with reference to each figure below:

[0037] As Figure 1 shown, a scissor-type variable Poisson's ratio folding and unfolding mechanism is composed of multiple rods hinged together and is symmetric about a straight line perpendicular to AH through I. According to the length, there are five types of rods, which are respectively marked as including the first B rod, the second B rod, the third B rod, the C rod and the D rod. Each of the rods is assembled into a basic unit.

[0038] The first end point of the rod AH is hinged to the first end point of the rod AC, and the connection point is marked as A;

[0039] The second end point of the rod AH and the rod G 1 The second end point of H are hinged, and the connection point is marked as H;

[0040] The second end point of the rod BD is hinged to the second end point of the rod CD, and the connection point is marked as D;

[0041] The first end point of the rod BD is hinged to a point on the rod AH, and the connection point is marked as B;

[0042] The second end point of the rod AC is hinged to the first end point of the rod CD, and the connection point is marked as C;

[0043] The first end point of the rod CE is hinged to the first end point of the rod EG, and the connection point is marked as E;

[0044] The first end point of the rod DF is hinged to a point on the rod EG, and the connection point is marked as F;

[0045] The second end point of the rod EG and the rod GH 1 The first end point of is hinged, and the connection point is marked as G;

[0046] The rod G 1 The midpoint of H and GH 1 The midpoint of is hinged, and the connection point is marked as I;

[0047] As Figure 3 Shown, it is a schematic structural diagram when the mechanism is compressed to the lowest in the negative Poisson's ratio stage. At this time, the angle between the GH 1 Rod and the positive x-axis direction is 11.771°. As Figure 4 Shown, it is a schematic structural diagram at the critical point of the positive and negative Poisson's ratio conversion of the mechanism. At this time, the angle between the GH 1 Rod and the positive x-axis direction is 90°. As Figure 5 Shown, it is a schematic structural diagram when the mechanism is compressed to the lowest in the positive Poisson's ratio stage. At this time, the angle between the GH 1 Rod and the positive x-axis direction is 168.229°. Assume that A 1 H 1 Is the static platform. When the angle between the GH 1 Rod and the positive x-axis direction is between 11.771° and 90°, while the mechanism elongates laterally, there is longitudinal expansion, that is, negative Poisson's ratio movement is carried out. When GH 1 The angle with the positive x-axis direction is between 90° and 168.229°, while the mechanism elongates laterally, there is longitudinal contraction, that is, the mechanism performs positive Poisson's ratio movement.

[0048] Furthermore, a circular expansion is carried out, which can be expanded into a regular 2n-sided polygon structure such as a quadrilateral, a hexagon, an octagon, etc. The corresponding angles of the first connecting member are 90°, 120°, 135°, etc. As Figure 2 shown, the basic unit and its horizontal mirror unit are connected by the first connecting member. In the basic unit, the first end point of rod A 1 H 1 is hinged to the first end point of the first connecting member. In the horizontal mirror unit, the first end point of rod A 3 H 3 is hinged to the second end point of the first connecting member. In the horizontal mirror unit, the first end point of rod A 2 H 2 is hinged to the first end point of the first connecting member. The first end point of rod AH in the assembly unit is hinged to the second end point of the first connecting member. The first connecting member is V-shaped, and the angle of the included angle of the V shape is consistent with the angle of the interior angle of the regular 2n-sided polygon structure. And so on, the assembly unit and the horizontal mirror unit are alternately connected to form a single-layer regular n-sided polygon scissor-type variable Poisson's ratio folding and unfolding mechanism, as Figure 6 shown.

[0049] Furthermore, an expansion in the column direction is carried out, as Figure 2 shown. The basic unit and its vertical mirror unit are connected by the second connecting member. The first end point of rod CE in the basic unit is hinged to the first end point of the second connecting member. In the vertical mirror unit, the first end point of rod C 1 E 1 is hinged to the second end point of the second connecting member. The first end point of C 1 E 1 is hinged to the first end point of the second connecting member. In the vertical mirror unit, the first end point of rod C 2 E 2 is hinged to the second end point of the second connecting member, forming a double-layer regular octagon scissor-type variable Poisson's ratio folding and unfolding mechanism, as Figure 7 shown, where 1 is the scissor-type variable Poisson's ratio folding and unfolding mechanism, 2 is its horizontal mirror image, and 3 is its vertical mirror image. Figure 8 is the schematic diagram of the positive Poisson's ratio structure of the double-layer expansion mechanism.

[0050] Furthermore, as Figure 9 shown, an n-layer expansion is carried out. Only the upper part of the uppermost layer and the lower part of the lowermost layer are connected by the first connecting member, and the middle layers are all connected by the second connecting member, finally forming an expansion in both the circular and column directions.

Claims

1. A scissor-type variable Poisson's ratio folding and unfolding mechanism, characterized in that: It includes a regular 2n-sided structure formed by connecting multiple basic units to each other, where n≥2. Each basic unit includes a first Z-shaped structure and a second Z-shaped structure. In each Z-shaped structure, the upper and lower ends of the C rod arranged obliquely are respectively hinged to two D rods arranged horizontally. The C rods of the two Z-shaped structures are cross-arranged at the middle position and hinged to each other at the cross position. The two upper D rods located above the two Z-shaped structures are coaxially arranged, and the two lower D rods located below the two Z-shaped structures are coaxially arranged. Between the outer ends of the lower D rods of the first Z-shaped structure and the D rods of the second Z-shaped structure, and between the outer ends of the upper D rods of the first Z-shaped structure and the lower D rods of the second Z-shaped structure, they are respectively connected by a parallelogram linkage mechanism. Each of the parallelogram linkage mechanisms includes two first B rods, two second B rods, and one third B rod. The two first B rods and the two second B rods have the same length. Among them, the two first B rods arranged horizontally and spaced apart are respectively hinged to the outer ends of the upper D rods of the first Z-shaped structure or the second Z-shaped structure and the rod segments of the upper D rods located inside the outer ends to form a first hinge point and a second hinge point. The two second B rods arranged horizontally and spaced apart are respectively hinged to the outer ends of the lower D rods of the first Z-shaped structure or the second Z-shaped structure and the rod segments of the lower D rods located inside the outer ends to form a third hinge point and a fourth hinge point. The inner end of the third B rod arranged horizontally is jointly hinged to the lower end of the first B rod located inside and the upper end of the second B rod located inside to form a fifth hinge point, and the outer end of the third B rod is jointly hinged to the lower end of the first B rod located outside and the upper end of the second B rod located outside to form a sixth hinge point. A first parallelogram structure of the parallelogram linkage mechanism is formed with the first hinge point, the second hinge point, the fifth hinge point, and the sixth hinge point as the four vertices of the quadrilateral. A second parallelogram structure of the parallelogram linkage mechanism is formed with the third hinge point, the fourth hinge point, the fifth hinge point, and the sixth hinge point as the four vertices of the quadrilateral; Between the ends of the two upper D rods located at the corners of the regular 2n-sided structure and between the ends of the two lower D rods in two adjacent basic units on the left and right are respectively connected by a first connecting piece. Among them, the two sides of the upper first connecting piece are respectively hinged to the two first hinge points at the corner positions of the two basic units. The two sides of the lower first connecting piece are respectively hinged to the two third hinge points at the corner positions of the two basic units. The first connecting piece is V-shaped, and the angle of the V-shaped angle is the same as the angle of the interior angle of the regular 2n-sided structure; Let the length of the first B member be k 1 , and the length of the second B member be k 2 , and the length of the third B member be k 3 , and the length of the C member be k 4 , where k i > 0, i = 1, 2, 3, 4, and k 1 = k 2 , 2k 1 > k 4 .

2. The scissor-type variable Poisson's ratio folding and unfolding mechanism according to claim 1, characterized in that: There are at least two of the regular 2n-sided polygon structures, and at least two regular 2n-sided polygon structures are stacked and connected up and down to form a regular 2n-sided polygon integrated multi-layer structure. In the regular 2n-sided polygon integrated multi-layer structure, the two lower D rods of each upper basic unit arranged in alignment up and down are respectively supported on the two upper D rods of the lower basic unit arranged in alignment, and the third hinge points and the first hinge points arranged corresponding to the upper and lower sides on the left and right sides in the two basic units at the stacking position are respectively jointly hinged to the second connecting member. In the regular 2n-sided polygon structure of the uppermost layer in the regular 2n-sided polygon integrated multi-layer structure, the outer ends of the adjacent sides of the two upper D rods located at the corner of the regular 2n-sided polygon structure in the two adjacent basic units on the left and right are connected by the upper first connecting member, and the two sides of the upper first connecting member are respectively hinged to the two first hinge points of the two upper D rods located at the corner of the regular 2n-sided polygon structure. And in the 2n-sided polygon structure of the lowermost layer, the outer ends of the adjacent sides of the two lower D rods located at the corner of the regular 2n-sided polygon structure in the two adjacent basic units on the left and right are connected by the lower first connecting member, and the two sides of the lower first connecting member are respectively hinged to the two third hinge points of the two lower D rods located at the corner of the regular 2n-sided polygon structure. The first connecting member is V-shaped, and the angle of the V-shaped included angle is consistent with the angle of the interior angle of the regular 2n-sided polygon structure.

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