A triangular prism space stretching arm combining a sarrus mechanism and a scissors mechanism

Abstract

The application discloses a triangular prism space stretching arm combined with Sarrus mechanism and scissors mechanism, belongs to the field of aerospace, and is characterized in that the whole stretching wall is composed of longitudinally stacked multiple unfolding units and is in the form of a regular triangular prism in the unfolded state. The planar scissors units are combined in the layout of a space triangular prism and are arranged on the three side surfaces of each unfolding unit in the form of a triangular prism, so that the bending resistance of the single planar scissors unit when bearing lateral force is avoided. The end portions of the scissors units are connected by sliding rails, so that the bending strength of the stretching arm is improved. Meanwhile, two longitudinally arranged Sarrus connecting rods are added to the three edges of the unfolding unit, and the transmission angle of the longitudinally arranged Sarrus connecting rods is 0, so that the stretching arm end is locked and the longitudinal bearing capacity of the whole stretching arm is improved. The stretching arm has the characteristics of high unfolding / folding ratio, high longitudinal bearing capacity, relatively simple structure and synchronous unfolding / folding.

Description

Technical Field

[0001] This invention relates to space deployable mechanisms in the aerospace field, specifically to a triangular prism space extendable arm that combines a Sarrus mechanism and a scissor mechanism. Background Technology

[0002] Space deployable mechanisms typically refer to mechanisms in which individual components gradually unfold from their original closed state during operation, supporting a designated tool to a specific position or being extended to a specific position by other mechanisms. They are key equipment in the field of space exploration. Space extension arms, as an important component of space deployable mechanisms, have been widely used in equipment components such as space robotic arms, solar panels, and deployable antennas. Therefore, they have broad application prospects in space platforms, space testing equipment, and various scientific research and testing satellites.

[0003] With the increasing emphasis on space exploration and the growing number of such activities, the demand for reachable arms is constantly increasing, and the requirements for their use are also rising. Typically, these mechanisms are required to have a high retraction-to-extension ratio to save space within the spacecraft, thereby facilitating the carrying of more payloads and scientific instruments. They are also required to possess high reliability, high rigidity and strength, and bending resistance to ensure the normal operation of the payload equipment.

[0004] With more large equipment entering space, this means that deployable booms face greater loads and longer deployment distances. This presents further challenges to the deployment-to-retraction ratio and strength specifications of new deployable booms. Existing deployable mechanism solutions are at risk of instability or even breakage under these challenges, risks that are seriously threatening the normal execution of aerospace missions. Summary of the Invention

[0005] To address the issue that existing extendable arms composed of multiple scissor lift units suffer from weak longitudinal load capacity because the longitudinal load is entirely borne by the scissor lift itself after full deployment, resulting in significant forces at the hinges, this invention proposes a triangular prism spatial extendable arm that combines a Sarrus mechanism and a scissor lift mechanism. This novel one-dimensional spatial extendable arm is designed based on a spatial triangular prism layout of scissor lift units combined with a Sarrus mechanism. For each triangular prism scissor lift unit, a Sarrus mechanism with virtual constraints is added to the three edges of the triangular prism to improve the longitudinal load capacity of the scissor lift mechanism. The extendable arm mechanism is constructed by longitudinally stacking scissor lift units combined with the Sarrus mechanism in a one-dimensional arrangement. This extendable arm features a high extension-to-retraction ratio, high longitudinal load capacity, relatively simple structure, and simultaneous extension and retraction.

[0006] This invention is a triangular prism spatial extension arm that combines the Sarrus mechanism and the scissor mechanism. It consists of several longitudinally stacked and connected deployment units, a drive unit, a drive motor, and a fixed base; the deployment units are in the right-hand triangular prism shape when deployed.

[0007] The unfolding unit has three sets of planar scissor mechanisms on its three circumferential side surfaces, and intermediate connectors at three included angles on its top circumferential surface. Adjacent connectors are connected by intermediate slide rails. The top ends of each planar scissor mechanism are connected to two intermediate connectors on the same side surface to form a revolute joint. Simultaneously, the three circumferential prisms of the unfolding unit have three sets of Sarrus links, the top ends of which are hinged to the three intermediate connectors to form revolute joints.

[0008] In the upper-level deployment unit, the bottom ends of three planar scissor mechanisms are connected to two intermediate connecting pieces on the same side in the lower-level deployment unit, forming revolute joints. In the bottommost deployment unit, the bottoms of three planar scissor mechanisms are connected to three base connecting pieces circumferentially arranged on the top surface of the fixed base, forming revolute joints. Simultaneously, the bottom ends of three Sarrus linkages are connected to three base connecting pieces, forming revolute joints; the three base connecting pieces are respectively mounted on three fixed base slide rails on the fixed base; and their directions of movement intersect at the midpoint of the base.

[0009] The drive unit has a lead screw that is fixedly threaded to the center of the base; the end of the lead screw is coaxially fixed to the output shaft of the drive motor. The lead screw nut is connected to three base connectors through three drive rods arranged at equal angles in the circumferential direction.

[0010] The spatial extension arm deployment process, combining the Sarrus mechanism and the triangular prism scissor mechanism, is as follows: The drive motor rotates the drive screw, causing the screw nut to rise relative to the fixed base. This rise, via the drive rod, moves the three base connectors towards the center of the fixed base, thereby driving the three sets of scissor mechanisms in the lowest-level deployment unit, hinged to the base connectors, to begin retracting. The entire deployment unit extends longitudinally, and the upper plane of the triangular prism rises. As the upper surface of the triangular prism rises, the included angle of the three Sarrus links gradually increases. During this process, the tops of the three sets of scissor mechanisms simultaneously drive the three sets of scissor mechanisms in the previous level to retract synchronously, and the three sets of Sarrus links to extend synchronously. Similarly, the retraction movement of the three sets of scissor mechanisms in the lower-level deployment unit can serve as the drive for the retraction of the three sets of scissor mechanisms in the upper-level deployment unit, ultimately enabling the synchronous deployment of each level of deployment unit. When all Sarrus links are angled at 180 degrees, the extension arm extends to its maximum length, completing the extension action; at this time, the Sarrus links are locked; during the above-mentioned deployment process, the horizontal distance between adjacent intermediate connecting parts in each level of the extension and retraction unit is shortened, and the intermediate slide rail between them retracts.

[0011] The advantages of this invention are:

[0012] 1. This invention combines the Sarrus mechanism and the scissor mechanism into a triangular prism spatial extension arm. By combining planar scissor units in a spatial triangular prism layout, it effectively utilizes the stability of triangles and avoids the weak bending resistance of a single planar scissor unit when subjected to lateral forces.

[0013] 2. The present invention combines a triangular prism spatial extension arm with a Sarrus mechanism and a scissor mechanism. It utilizes a motor-driven lead screw mechanism to drive a connecting rod slider mechanism to extend and retract the deployment mechanism, so that each deployment unit can extend and retract synchronously.

[0014] 3. This invention combines a Sarrus mechanism and a scissor mechanism in a triangular prism spatial extension arm. For each triangular prism-shaped deployment unit, two hinged longitudinal Sarrus links are added to each of its three edges, thus forming a Sarrus mechanism within the deployment unit. After full extension, the characteristic that the transmission angle of the longitudinal Sarrus links is 0° creates a deadlock on the movement at the end of the extension arm, thereby improving the longitudinal load-bearing capacity of the entire extension arm.

[0015] 4. The present invention combines a triangular prism spatial extension arm with a Sarrus mechanism and a scissor mechanism. A slide rail is added between the two rotating joints. During the extension and retraction of the extension arm, the slide rail restricts the two rotating joints to move only horizontally relative to each other, thereby improving the bending strength of the extension arm. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the fully extended state of the triangular prism spatial extension arm of the present invention, which combines the Sarrus mechanism and the scissor mechanism.

[0017] Figure 2 This is a schematic diagram of the drive unit structure in the triangular prism spatial extension arm that combines the Sarrus mechanism and the scissor mechanism of the present invention.

[0018] Figure 3 This is a schematic diagram of the double rotary joint structure of the drive unit;

[0019] Figure 4 This is a schematic diagram of a single deployable unit structure in the triangular prism spatial extension arm that combines the Sarrus mechanism and the scissor mechanism of the present invention.

[0020] Figure 5 This is a schematic diagram of the intermediate slide rail structure of the double rotating joint in the unfolded unit;

[0021] Figure 6 This is a schematic diagram showing the connection method between two adjacent unfolding units in the triangular prism spatial extension arm that combines the Sarrus mechanism and the scissor mechanism of the present invention.

[0022] Figure 7 This is a schematic diagram of the fully retracted triangular prism spatial extension arm of the present invention, which combines the Sarrus mechanism and the scissor mechanism.

[0023] In the picture:

[0024] 1-Deployment unit 2-Drive mechanism 3-Drive motor

[0025] 4-Fixed base 101-Expanding unit double rotating joint 102-Double rotating joint intermediate slide rail

[0026] 102a - Outer slide rail; 102b - Inner slide rail; 102c - Connecting plate

[0027] 102d - Track 103 - Sarrus upper link 104 - Sarrus lower link

[0028] 105-Scissor lift lever; 201-Drive unit double rotary joint; 202-Drive unit slide rail

[0029] 203-Drive unit slider; 204-Drive rod; 205-Drive screw

[0030] 206 - Lead screw nut; 401 - Slot; 402 - Drive mounting hole Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings.

[0032] The triangular prism spatial extension arm of this invention, which combines a Sarrus mechanism and a scissor mechanism, mainly consists of several longitudinally stacked deployment units 1, a drive unit 2, a drive motor 3, and a fixed base 4, as shown below. Figure 1 As shown, this embodiment is designed with a spatial extension arm consisting of two deployment units.

[0033] like Figure 2 As shown, the fixed base 4 is an isosceles triangular plate with circumferential openings for screws to fix it to external equipment, ensuring it remains stationary throughout the extension and retraction of the arm. The fixed base 4 has three equally spaced slots 401 circumferentially arranged along the midpoints of the three included angles of the fixed base. A drive mounting hole 402 is located at the center of the fixed base 4, through which the drive unit 2 is mounted.

[0034] The drive unit 2 includes three drive mechanisms, three drive rods 204, and one drive screw 205. The three drive mechanisms are structurally identical, each including a drive unit double rotary joint 201, a drive unit slide rail 202, and a drive unit slider 203. In the three drive mechanisms, the drive unit slide rails 202 are respectively arranged along three circumferential slots 401 of the fixed base 4, and are embedded and fixed within the slots 401. The drive unit sliders 203, which slide along the drive unit slide rails 202, are slidably connected to the three drive unit slide rails 202; the drive unit double rotary joints 201 are fixedly mounted on the top surface of the drive unit sliders 203.

[0035] like Figure 3 As shown, the drive unit double rotary joint 201 has a base plate 201a. The lower surface of the base plate 201a is fitted to the top surface of the drive unit slider 203, and the two are fixed by bolts, so that the drive unit double rotary joint 201 can move along the drive unit slide rail 202 with the drive unit slider 203. The upper surface of the base plate 201a is designed with a V-shaped connector 201b composed of left and right side plates and a U-shaped connector 201c whose inner side of the V-shaped connector 201b is connected to the base plate 201a; and the midpoint of the included angle between the two side plates of the V-shaped connector 201b is arranged along the sliding direction of the drive unit slider 203, parallel to the midpoint of the U-shaped cross-section of the U-shaped connector 201c, and located in a plane perpendicular to the base plate 201a. The U-shaped connector 201c is used to connect to the drive screw 205 through the drive rod 204; the V-shaped connector 201b is used to connect to the unfolding unit 1 through the rotary joint.

[0036] The drive screw 205 is coaxially placed in the drive mounting hole 402 on the base plate and fixed to the fixed base 4 through the connecting flange coaxially threaded on the drive screw 205. A screw nut 206 is threaded onto the drive screw 205, and three U-shaped joints are evenly distributed around the screw nut. The three U-shaped joints are respectively connected to the output ends of the three drive rods 204 to form a rotating pair. The other ends of the three drive rods 204 are respectively connected to the U-shaped connecting parts in the aforementioned three drive unit double rotating pairs 201 to form a rotating pair. The bottom end of the drive screw 205 is coaxially fixed to the output shaft of the drive motor 3 through a coupling. The drive motor 3 is fixedly mounted on the bottom surface of the fixed base 4 through a motor frame. Thus, the rotation of the drive motor 3 drives the drive screw 205 to rotate, which in turn drives the screw nut 206 to move axially along the drive screw 205. Finally, the three drive rods 204 drive the three drive unit double rotating joints 201 to move along the three sliders toward or away from the center of the fixed base 4, thereby realizing the extension and retraction control of the unfolding mechanism 1 with the three drive unit double rotating joints 201.

[0037] like Figure 4As shown, the unfolding unit 1 consists of three unfolding unit double rotating joints 101, three sets of double rotating joint intermediate slide rails 102, three Sarrus connecting rods (upper rods) 103, three Sarrus connecting rods (lower rods) 104, and six scissor rods 105. When fully unfolded, the unfolding unit 1 has an equilateral triangular prism shape. The three unfolding unit double rotating joints 101 are respectively arranged at the vertices of the triangles on the top surface of the triangular prism, and their structure is the same as that of the V-shaped connector 201b in the aforementioned drive unit double rotating joint 201. Furthermore, the intersection point of the midpoints of the included angles of the two side plates is located on the axis of the triangular prism.

[0038] In the three unfolding unit double rotating joints 101, adjacent side plates of adjacent unfolding unit double rotating joints 101 are connected by a double rotating joint intermediate slide rail 102. For example... Figure 5 As shown, the double-rotor intermediate slide rail 102 consists of an outer slide rail 102a and an inner slide rail 102b. The bottom of both slide rails is a connecting plate 102c, and the upper part is a U-shaped cross-section track 102d; the track 102d of the outer slide rail 102a is embedded inside the track 102d of the inner slide rail 102a, and the two are slidably connected. One end of the connecting plate 102c of the outer slide rail 102a is fixedly connected to one side plate; the opposite end of the connecting plate of the inner slide rail 102b is designed with a boss that is fixedly connected to the other side plate.

[0039] Furthermore, scissor bar connection holes are provided at corresponding positions on the upper and lower parts of the two side plates of the three unfolding unit double rotating joints 101 for connecting scissor bars 105. The six scissor bars 105 are centrally hinged in pairs to form a planar scissor mechanism. The three sets of planar scissor mechanisms are arranged on the three sides of the triangular prism. The tops of the two scissor bars 105 in each planar scissor mechanism are respectively connected to the scissor bar connection holes below the adjacent side plates of the two unfolding unit double rotating joints 101 on their respective sides via rotating shafts to form a rotating joint.

[0040] Furthermore, a Sarrus connecting rod, consisting of an upper Sarrus connecting rod 103 and a lower Sarrus connecting rod 104, is connected at the included angle of the two side plates in the double rotating joint 101 of the three unfolding units. The three sets of Sarrus connecting rods are located at the longitudinal edges of the triangular prism. In each set of Sarrus connecting rods, the bottom end of the upper Sarrus connecting rod 103 and the top end of the lower Sarrus connecting rod 104 are connected by a pivot to form a rotating joint; the top end of the upper Sarrus connecting rod 103 is inserted into a slot designed at the included angle of the two side plates in the double rotating joint 101 of the unfolding unit. Corresponding upper and lower positions in the slot are designed with connecting rod connecting holes, wherein the lower connecting rod connecting hole is connected to the top end of the upper Sarrus connecting rod 103 through a pivot to form a rotating joint.

[0041] The aforementioned spatial extension arm can have two or more deployment units 1, which can be arranged as needed. Multiple deployment units can be combined longitudinally and installed on the fixed base 4 to obtain an extension arm with a larger deployment length. The combination method between adjacent deployment units 1 and their installation method with the fixed base 4 are as follows:

[0042] like Figure 6 As shown, in adjacent deployment units 1, the bottom ends of two scissor rods 105 in the planar scissor mechanism arranged on the three sides of the triangular prism in the upper deployment unit 1 are respectively connected to the scissor rod connection holes above the adjacent side plates of the two deployment unit double rotating joints 101 in the lower deployment unit 1 on the same side through rotating shafts to form rotating joints. At the same time, the bottom ends of the lower rods 104 of the three sets of Sarrus connecting rods in the upper deployment unit 1 are respectively inserted into the slots at the included angles of the two side plates of the three deployment unit double rotating joints 101 in the lower deployment unit 1, and are connected to the upper scissor rod connection holes at the slots of the deployment unit double rotating joints 101 through rotating shafts to form rotating joints.

[0043] This enables the vertical stacking of multiple unfolding units 1. In the lowest unfolding unit 1, the bottom ends of two scissor rods 105 in the planar scissor mechanism arranged on the three sides of the triangular prism are connected to the base connection holes on the adjacent side plates of the V-shaped connectors 201b in the adjacent drive unit double rotating joints 201 of the fixed base 4, forming rotating joints. Simultaneously, the bottom ends of the lower rods 104 of the three sets of Sarrus linkages in the lowest unfolding unit 1 are inserted into the slots at the included angles of the side plates of the V-shaped connectors 201b in the three drive unit double rotating joints 201 of the fixed base 4, and connected by a rotating shaft to form rotating joints, thus realizing the connection between the unfolding unit 1 and the fixed base 4.

[0044] Through the above design, the double rotary joint 205 of the drive mechanism will move linearly along the slide rail 202 of the drive unit after being driven by the drive rod 204. At this time, the scissor bar 105 and the lower rod 104 of the Sarrus connecting rod in the lowest layer deployment unit 1 will rotate accordingly, and the movement of the lower layer deployment unit 1 can serve as the drive for the upper layer deployment unit, thereby realizing the synchronous deployment and retraction of each layer deployment unit of the extension arm. Specifically:

[0045] When the spatial extension arm of this invention is ready to unfold, the drive motor 3 drives the drive screw 205 to rotate, and the screw nut 206 rises relative to the fixed base 4. Through the drive rod 204, it drives the three drive mechanism double rotating joints 205 to move towards the center of the fixed base 4, thereby driving the three sets of scissor mechanisms of the lowest level (first level) unfolding unit 1, which are hinged to the drive mechanism double rotating joints 205, to begin to retract. The overall unfolding unit 1 extends longitudinally, and the upper plane of the triangular prism rises. As the upper surface of the triangular prism rises, the angle between the upper rod 103 and the lower rod 104 of the three sets of Sarrus links gradually increases. During the above process, the top of the three sets of scissor mechanisms also simultaneously drives the three sets of scissor mechanisms of the previous level to retract synchronously, and the three sets of Sarrus links to extend synchronously. By analogy, it can be seen that the retraction movement of the three sets of scissor mechanisms in the lower level unfolding unit 1 can serve as the driving force for the retraction movement of the three sets of scissor mechanisms in the upper level unfolding unit 1, ultimately enabling the unfolding units 1 of each level to unfold synchronously. When the angle between all the articulated Sarrus links, upper link 103 and lower link 104, is 180 degrees, the extendable arm extends to its maximum length, completing the extension action. At this time, the Sarrus link locks. After locking, it can bear the longitudinal load to improve the longitudinal load-bearing capacity of the entire extendable arm.

[0046] During the aforementioned deployment process, the horizontal distance between the double rotating joints 101 of adjacent deployment and retraction units 1 at each level is shortened, and the intermediate slide rail 102 of the double rotating joint between them contracts. Through the design of the U-shaped cross-section track 102d with the outer slide rail 102a and the inner slide rail 102a nested and sliding together, the double rotating joints 101 of the deployment and retraction unit are restricted to sliding relative to each other in the horizontal direction during the deployment and retraction process. After being fully deployed, the longitudinal movement of the double rotating joints 101 of the deployment and retraction unit is restricted, thereby improving the bending resistance of the extension arm in the deployed state.

[0047] The retraction process drives motor 3 to rotate in the opposite direction, which is the reverse of the unfolding process. The retracted state is as follows: Figure 7 As shown.

Claims

1. A triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism, characterized in that: It consists of several vertically stacked and connected unfolding units, a drive unit, a drive motor, and a fixed base; The unfolded unit is a right triangular prism in its unfolded state; The unfolding unit has three sets of planar scissor mechanisms on its three circumferential side surfaces, and intermediate connectors at the three included angles on its top surface. Adjacent connectors are connected by intermediate slide rails. The top two ends of each planar scissor mechanism are respectively connected to two intermediate connectors on the same side to form a revolute joint. At the same time, the three circumferential prisms of the unfolding unit have three sets of Sarrus links, and the top ends of the three sets of Sarrus links are respectively hinged to the three intermediate connectors to form a revolute joint. In the upper-level unfolding unit, the bottom ends of the three sets of planar scissor mechanisms are respectively connected to two intermediate connecting parts on the same side in the lower-level unfolding unit to form a rotating pair; In the lowest unfolding unit, the bottom of the three planar scissor mechanisms is connected to the three base connectors arranged circumferentially on the top surface of the fixed base to form a rotating pair; at the same time, the bottom ends of the three Sarrus linkages are connected to the three base connectors to form a rotating pair; the three base connectors are respectively installed on the three base slide rails fixedly installed on the fixed base; and the directions of movement intersect at the midpoint of the base. The drive unit has a drive screw that is fixedly threaded to the center of the base; the end of the drive screw is coaxially fixed to the output shaft of the drive motor; the screw nut on the drive screw is connected to three base connectors through three drive rods arranged at equal angles in the circumferential direction.

2. The triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism as described in claim 1, characterized in that: The three slide rails are respectively embedded in the three grooves opened on the base.

3. The triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism as described in claim 1, characterized in that: The drive screw is coaxially placed in the center hole of the fixed base and fixed to the fixed base through the connecting flange with coaxial thread on the drive screw.

4. The triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism as described in claim 1, characterized in that: The base connector is a double rotary joint connector, with a base plate connecting to the base slide rail; the upper surface of the base plate is designed with a V-shaped connector composed of left and right side plates and a U-shaped connector whose inner side connects to the base plate; the midpoint of the included angle between the two side plates of the V-shaped connector is arranged along the sliding direction of the slider of the drive unit, parallel to the midpoint of the U-shaped cross-section of the U-shaped connector, and located in a plane perpendicular to the base plate; the U-shaped connector is used to connect to the drive screw through the drive rod; the V-shaped connector is used to connect to the unfolding unit through the rotary joint.

5. A triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism as described in claim 1, characterized in that: The intermediate connector is a double rotating joint connector, a V-shaped connector composed of left and right side plates. The intersection point of the midpoint of the included angle of the two side plates is located on the axis of the triangular prism. The two side plates of the intermediate connector are designed with through holes at corresponding positions on the upper and lower sides, which are respectively connected to the planar scissor mechanism in the upper and lower unfolding units through rotating joints.

6. A triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism as described in claim 1, characterized in that: The middle slide rail consists of an outer slide rail and an inner slide rail; the bottom of the two slide rails is a connecting plate, and the upper part is a U-shaped cross-section track; the track of the outer slide rail is embedded inside the track of the inner slide rail, and the two are slidably connected; one end of the connecting plate of the outer slide rail is fixedly connected to an intermediate connecting piece; the opposite end of the connecting plate of the inner slide rail is designed with a boss and fixedly connected to another intermediate connecting piece.

7. A triangular prism spatial extension arm combining a Sarrus mechanism and a scissor mechanism as described in claim 1, characterized in that: The unfolding process is as follows: The drive motor drives the drive screw to rotate, and the screw nut rises relative to the fixed base. This, through the drive rod, drives the three base connectors to move towards the center of the fixed base, thereby driving the three sets of scissor mechanisms of the lowest-level unfolding unit, which are hinged to the base connectors, to begin retracting. The overall unfolding unit extends longitudinally, and the upper plane of the triangular prism rises. As the upper surface of the triangular prism rises, the included angle of the three sets of Sarrus links gradually increases. During the above process, the tops of the three sets of scissor mechanisms also simultaneously drive the three sets of scissor mechanisms of the previous level to retract synchronously, and the three sets of Sarrus links to extend synchronously. Similarly, the retraction movement of the three sets of scissor mechanisms in the lower-level unfolding unit can serve as the drive for the retraction of the three sets of scissor mechanisms in the upper-level unfolding unit, ultimately enabling the unfolding units at all levels to unfold synchronously. When the included angle of all Sarrus links is 180 degrees, the extension arm extends to its maximum length, completing the extension action. At this time, the Sarrus links are locked. During the above unfolding process, the horizontal distance between adjacent intermediate connectors in each level of unfolding unit shortens, and the intermediate slide rail between them retracts.

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