A mechanical extension device

Abstract

The present invention provides a mechanical stretching device, wherein the mechanical stretching device includes: a seat unit, which includes a mounting plate, and a mounting plane is arranged on the mounting plate; a connecting rod structure, which is connected to the mounting plate through a first rivet point and a second rivet point on the mounting plate; and a leg unit, which is connected to the mounting plate through a third rivet point and a fourth rivet point on the mounting plate; the first rivet point, the second rivet point and the third rivet point are all located below the mounting plane; the vertical distance between the center of the fourth rivet point and the extension line of the mounting plane of the mounting plate does not exceed 10 mm.

Description

Technical Field

[0001] The invention relates to a mechanical stretching device. Background Art

[0002] In the existing sofas, seats or wheelchairs, an electric or manual mechanical extension device is usually installed inside, which can realize the adjustment of the sofa, seat or wheelchair, so that the sofa, seat or wheelchair can be switched between different states. The mechanical extension device for the armrest floor sofa in the prior art includes a seat unit, a leg unit, a backrest unit, a connecting rod structure and a driving unit, which controls the extension of the leg unit and the angle adjustment of the backrest unit through the driving unit. The mechanical extension device for the armrest floor sofa in the prior art has the following disadvantages: the coordination design of the leg unit and the connecting rod structure with the seat unit is unreasonable, resulting in a high overall height of the mechanical extension device, which is not conducive to size control; the seat unit is equipped with a connecting component for installing a wooden frame, and its structure is relatively complex; in order to reduce the seat height, the wooden frame is sunken and installed on the inner side of the mounting plate of the seat unit, and there is a certain gap between it and the inner side of the mounting plate, which is easy to accumulate dust and damage and has poor stability; the structural design of the connecting rod structure is unreasonable, resulting in insufficient smoothness of operation, affecting the user experience; the structural strength of the backrest unit is low, resulting in easy damage during use. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a mechanical stretching device with a reasonable structural design.

[0004] The technical solution adopted by the embodiment of the present invention to solve the above problem is: a mechanical stretching device, characterized in that it includes:

[0005] A seat unit, comprising a mounting plate, a mounting plane being arranged on the mounting plate, and a first riveting point, a second riveting point, a third riveting point and a fourth riveting point being provided on the mounting plate;

[0006] A connecting rod structure connected to the mounting plate via a first rivet point and a second rivet point on the mounting plate; and

[0007] a leg unit connected to the mounting plate via a third rivet point and a fourth rivet point on the mounting plate;

[0008] The first riveting point, the second riveting point and the third riveting point are all located below the mounting plane; and the vertical distance between the center of the fourth riveting point and the extension line of the mounting plane of the mounting plate does not exceed 10 mm.

[0009] In the embodiment of the present invention, the center of the fourth riveting point is located above the mounting plane and the vertical distance between the center of the fourth riveting point and the extension line of the mounting plane of the mounting plate does not exceed 1 mm.

[0010] The connecting rod structure described in the embodiment of the present invention includes a first connecting rod, a second connecting rod and a third connecting rod, wherein one end of the first connecting rod is hinged at the first rivet point of the mounting plate, and the other end thereof is hinged to the third connecting rod; one end of the second connecting rod is hinged at the second rivet point of the mounting plate, and the other end thereof is hinged to the third connecting rod; the first connecting rod, the second connecting rod, the third connecting rod and the mounting plate constitute a first four-link structure.

[0011] An embodiment of the present invention also includes a control structure, which includes a first control link, a second control link, a third control link and a fourth control link; wherein one end of the second control link is hinged to the first control link, and the other end thereof is hinged to the third control link; one end of the fourth control link is hinged to the first control link, and the other end thereof is hinged to the third control link; the first control link, the second control link, the third control link and the fourth control link form a second four-bar structure.

[0012] The control structure described in the embodiment of the present invention also includes a fifth control link, a sixth control link and a seventh control link; wherein one end of the fifth control link is hinged to the fourth control link, and the other end thereof is hinged to the third link; one end of the sixth control link is hinged to the second control link, and the other end thereof is hinged to the third link; one end of the seventh control link is hinged to one end of the second control link, and the other end thereof is hinged to the third link.

[0013] An embodiment of the present invention also includes a backrest unit, which includes a fixed plate, a first backrest adjustment rod, a second backrest adjustment rod, a third backrest adjustment rod and a fourth backrest adjustment rod, wherein the fixed plate is fixed to the mounting plate, one end of the first backrest adjustment rod is hinged to the fixed plate; the third backrest adjustment rod is hinged to the fixed plate and has the first arm and the second arm; one end of the second backrest adjustment rod is hinged to the first backrest adjustment rod, and the other end thereof is hinged to the first arm of the third backrest adjustment rod; the second arm of the third backrest adjustment rod is hinged to the fourth backrest adjustment rod, and the fourth backrest adjustment rod is hinged to the first control link.

[0014] The leg unit of the embodiment of the present invention comprises a first leg adjustment rod, a second leg adjustment rod, a third leg adjustment rod, a fourth leg adjustment rod, a fifth leg adjustment rod, a sixth leg adjustment rod and a seventh leg adjustment rod; one end of the first leg adjustment rod is hinged to the fourth leg adjustment rod, and the first leg adjustment rod is hinged to the second leg adjustment rod at its middle position; the third leg adjustment rod has a first hinge point, a second hinge point and a third hinge point, one end of the second leg adjustment rod is hinged to the first hinge point of the third leg adjustment rod, and the fourth leg adjustment rod is hinged to the The second hinge point of the third leg adjustment rod, the other end of the fourth leg adjustment rod relative to the first leg adjustment rod is hinged to the sixth leg adjustment rod; one end of the fifth leg adjustment rod is hinged at the third hinge point of the third leg adjustment rod, and the other end of the fifth leg adjustment rod is hinged to the seventh leg adjustment rod; one end of the seventh leg adjustment rod is hinged to the third rivet point of the mounting plate; one end of the sixth leg adjustment rod is hinged at the fourth rivet point of the mounting plate, and the middle position of the sixth leg adjustment rod is hinged to the middle position of the fifth leg adjustment rod.

[0015] The leg unit of the embodiment of the present invention further comprises a linkage adjustment rod, one end of which is hinged to the third connecting rod, and the other end of which is hinged to the seventh leg adjustment rod.

[0016] An embodiment of the present invention also includes a driving unit, which includes a first bracket, a second bracket and a telescopic unit, wherein both ends of the telescopic unit are respectively connected to the first bracket and the second bracket; the first bracket is connected to the first control link; and the second bracket is connected to the seventh leg adjustment rod.

[0017] When the embodiment of the present invention is in a sitting state, the intersection point of the extension line of the installation plane and the extension line of the outer side of the leg unit is A. When the mechanical extension device is in a sitting state, the distance between the intersection point A and the ground is between 255mm and 264mm.

[0018] In the embodiment of the present invention, when the mechanical extension device is installed on any one of a sofa, a seat or a wheelchair, and any one of the sofa, the seat or the wheelchair is placed on a horizontal plane, the angle between the installation plane and the horizontal plane is 5 degrees to 10 degrees.

[0019] In the embodiment of the present invention, at least one set of clearance holes is provided on the first control link.

[0020] Compared with the prior art, the present invention has one or more of the following advantages or effects: simple structure and reasonable design; the seat frame can be adjusted to various states with only one power unit, and the cost is relatively low; the connecting rod structure and the control structure are more compact and more reasonably designed, so that the adjustment operation is smoother and the comfort of use is improved; the structural strength of the backrest unit is improved and it is not easy to be damaged during use; by setting the positions of the first riveting point, the second riveting point, the third riveting point and the fourth riveting point, the overall height of the sofa can be reduced to meet the demand for a low seat height, and further, the overall thickness of the mechanical extension device can be reduced, that is, the space at the bottom of the sofa can be increased while the seat height remains unchanged, so that its application direction can be extended to high-legged sofas or sofas with storage functions; the wooden frame can be directly installed on the installation plane, and there is no gap between the wooden frame and the side of the installation plate, so the stability is enhanced and the installation is more convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 The three-dimensional structure of the mechanical stretching device in the embodiment of the present invention is shown in FIG. Figure 1 , showing the mechanical extension device in a sitting position.

[0023] Figure 2 The three-dimensional structure of the mechanical stretching device in the embodiment of the present invention is shown in FIG. Figure 2 , showing the mechanical extension device in a sitting position.

[0024] Figure 3 It is a schematic diagram of the coordination of the seat unit, the connecting rod structure, the foot unit, the backrest unit and the control structure, showing the sitting position.

[0025] Figure 4 It is a schematic diagram of the coordination of the seat unit, the connecting rod structure, the foot unit, the backrest unit and the control structure, showing the state of being in a leisure posture.

[0026] Figure 5 This is a schematic diagram of the coordination of the seat unit, connecting rod structure, foot unit, backrest unit and control structure. Figure 1 , showing that it is in a lying position.

[0027] Figure 6 This is a schematic diagram of the coordination of the seat unit, connecting rod structure, foot unit, backrest unit and control structure. Figure 2 , showing that it is in a lying position.

[0028] Figure 7 This is a schematic diagram of the coordination of the seat unit, connecting rod structure, foot unit, backrest unit and control structure. Figure 3 , showing that it is in a lying position.

[0029] Figure 8 yes Figure 5 Enlarged view of point A in the middle.

[0030] Fig. 9 yes Figure 2 Enlarged view of point B in the middle. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0032] See also Figures 1 to 9 The mechanical extension device of this embodiment can be applied to sofas, chairs or wheelchairs, and is particularly applicable to electric sofas with floor-standing armrests, and includes a seat unit 1, a leg unit 2, a backrest unit 3, a connecting rod structure 4, a control structure 5 and a drive unit 6. The connecting rod structure 4 and the control structure 5 form a suspension mechanism of the mechanical extension device.

[0033] The seat unit 1 in this embodiment includes a mounting plate 11. A mounting plane 111 is disposed on the upper portion of the mounting plate 11. The mounting plane 111 is directly formed on the mounting plate 11 by bending and is used to mount the wooden frame 7. Specifically, the wooden frame 7 can be directly placed on the mounting plane 111 for fixing. When the mechanical extension device is mounted on any one of a sofa, a seat or a wheelchair, and any one of the sofa, the seat or the wheelchair is placed on a horizontal plane, the angle a between the mounting plane and the horizontal plane is 5 to 10 degrees.

[0034] The connecting rod structure 4 (suspension mechanism) in this embodiment is connected to the mounting plate 11 through the first rivet point 1111 and the second rivet point 1112 on the mounting plate 11. The leg unit 2 in this embodiment is connected to the mounting plate 11 through the third rivet point 1113 and the fourth rivet point 1114 on the mounting plate 11. Figure 3 As shown, when in use, the first riveting point 1111 , the second riveting point 1112 and the third riveting point 1113 are all located below the mounting plane 111 .

[0035] In some embodiments, when the mechanical stretching device is in use, the vertical distances between the first rivet point 1111, the second rivet point 1112, the third rivet point 1113, and the fourth rivet point 1114 and the mounting plane 111 of the mounting plate 11 (or the vertical distances of the extension line of the mounting plane 111) are no more than 20 mm. In some embodiments, when the mechanical stretching device is in use, the vertical distance between the fourth rivet point 1114 and the extension line of the mounting plane 111 of the mounting plate 11 is no more than 10 mm. In some embodiments, when the mechanical stretching device is in use, the center of the fourth rivet point 1114 is located above the mounting plane and the vertical distance between the center of the fourth rivet point 1114 and the extension line of the mounting plane 111 of the mounting plate 11 is no more than 1 mm.

[0036] Preferably, in some embodiments, when the mechanical stretching device is in use, the fourth rivet point 1114 is located within 10 mm above the mounting plane 111 or within 10 mm above the extension line in the length direction. More preferably, in some embodiments, when the mechanical stretching device is in use, the fourth rivet point 1114 is located within 1 mm above the mounting plane 111 or within 1 mm above the extension line in the length direction. Further preferably, in some embodiments, when the mechanical stretching device is in use, the fourth rivet point 1114 is not lower than the mounting plane 111 in the extension direction of the length direction of the mounting plane 111, that is, in the projection along the length direction of the mounting plane 111, the fourth rivet point 1114 coincides with the mounting plane 111 or is not more than 1 mm higher than the mounting plane. The distance in this embodiment refers to the vertical distance from the center point or center of the riveted point to the mounting plane 111 or the extension line of the mounting plane 111.

[0037] like Figure 3 As shown, in this embodiment, in the sitting state, the intersection point of the extension line of the installation plane 111 and the extension line of the outer side of the leg unit 2 is A. When the mechanical stretching device is in use, the distance H between the intersection point A and the ground is between 255 mm and 264 mm.

[0038] The connecting rod structure 4 in this embodiment is connected to the mounting plate 11, and specifically includes a first connecting rod 41, a second connecting rod 42 and a third connecting rod 43. The suspension mechanism is connected through the first connecting rod 41 and the second connecting rod 42 and is used for the mechanical extension device. Among them, one end of the first connecting rod 41 is hinged to the mounting plate 11. Specifically, one end of the first connecting rod 41 is hinged to the first rivet point 1111 of the mounting plate 11. Further, one end of the first connecting rod 41 is directly hinged to the first rivet point 1111 of the mounting plate 11 through a rivet. The first hinge point 1111 is located below the mounting plane 111, and the vertical distance between the first hinge point 1111 and the mounting plane 111 is less than 20mm, 15mm or 13mm, and the other end of the first connecting rod 41 The second connecting rod 42 is hinged to the mounting plate 11. Specifically, one end of the second connecting rod 42 is hinged to the second rivet point 1112 of the mounting plate 11. Further, one end of the second connecting rod 42 is directly hinged to the first rivet point 1112 of the mounting plate 11 through a rivet, and the vertical distance between the second hinge point 1112 and the mounting plane 111 is less than 20mm, 15mm or 13mm, and the other end of the second connecting rod 42 is hinged to the third connecting rod 43. The hinge points of the first connecting rod 41 and the third connecting rod 43 and the hinge points of the second connecting rod 42 and the third connecting rod 43 are respectively located at the two ends of the third connecting rod 43. The leg unit 2 in this embodiment also includes a linkage adjustment rod 28, which is connected to the leg unit 2, so that the connecting rod structure 4 and the leg unit 2 are linked. The first connecting rod 41 in this embodiment is roughly "1" shaped.

[0039] In this embodiment, the first connecting rod 41, the second connecting rod 42, the third connecting rod 43 and the mechanical extension device (mounting plate 11) connected thereto form a first four-link structure.

[0040] The backrest unit 3 in this embodiment is arranged on the mounting plate 11 . It specifically includes a fixed plate 31, a first backrest adjustment rod 32, a second backrest adjustment rod 33, a third backrest adjustment rod 34 and a fourth backrest adjustment rod 35, wherein the fixed plate 31 is fixed on the mounting plate 11, the first backrest adjustment rod 32 has a mounting portion 321 for mounting a backrest, one end of the first backrest adjustment rod 32 is hinged on the fixed plate 31, and when the first backrest adjustment rod 32 rotates around the hinge point between the fixed plate 31 and the fixed plate 31, the angle of the mounting portion 321 can be adjusted; the third backrest adjustment rod 34 is hinged on the fixed plate 31 and has a first arm 341 and a second arm 342; one end of the second backrest adjustment rod 33 is hinged to the first backrest adjustment rod 32, and the other end thereof is hinged to the first arm 341 of the third backrest adjustment rod 34; the second arm 342 of the third backrest adjustment rod 34 is hinged to the fourth backrest adjustment rod 35; the fourth backrest adjustment rod 35 is connected to the control structure 5, so as to realize the linkage between the control structure 5 and the backrest unit 3.

[0041] The fixing portion 31 in this embodiment is in a "U" shape. Specifically, the fixing portion 31 includes a main body 311, a first support arm 312 and a second support arm 313, the first backrest adjustment rod 32 is hinged to the first support arm 312, and the third backrest adjustment rod 34 is hinged to the second support arm 313. A reinforcing rib 314 is provided on the fixing portion 31, and the reinforcing rib 314 is provided on the main body 311 and extends at least to the first support arm 312. Furthermore, the reinforcing rib 314 extends to the second support arm 313. When in use, the first support arm 312 will bear the weight of the user when leaning on it. Therefore, the provision of the reinforcing rib 314 can increase the weight that the backrest unit 3 can bear and improve the structural strength.

[0042] The control structure 5 in this embodiment includes a first control link 51, a second control link 52, a third control link 53, a fourth control link 54, a fifth control link 55, a sixth control link 56 and a seventh control link 57; the fourth backrest adjustment rod 35 is hinged to the first control link 51, so as to realize the linkage between the control structure 5 and the backrest unit 3; one end of the second control link 52 is hinged to the first control link 51, and the other end thereof is hinged to the third control link 53; one end of the fourth control link 54 is hinged to the first control link 51, and the other end thereof is hinged to the third control link 53; the first control link 51, the second control link 52, the third control link 53 and the fourth control link 54 form a second four-bar structure.

[0043] In this embodiment, at least one set of clearance holes 511 is provided on the first control link 51, so as to facilitate the tightening of the screws below the first control link 51. In this embodiment, a notch 431 is provided on the third link 43, and the notch 431 corresponds to the clearance holes 511 to play a clearance role.

[0044] The control structure 5 in this embodiment is connected to the connecting rod structure 4 to achieve linkage. Specifically, one end of the fifth control connecting rod 55 is hinged to the fourth control connecting rod 54 (hinged at the middle position of the fourth control connecting rod 54), and the other end thereof is hinged to the third connecting rod 43; one end of the sixth control connecting rod 56 is hinged to the second control connecting rod 52 (hinged at the middle position of the second control connecting rod 52), and the other end thereof is hinged to the third connecting rod 43; one end of the seventh control connecting rod 57 is hinged to one end of the second control connecting rod 52, and the other end thereof is hinged to the third connecting rod 43. In this way, the linkage of the control structure 5 and the connecting rod structure 4 is achieved.

[0045] The leg unit 2 in this embodiment is connected to the mounting plate 11. The leg unit 2 specifically includes a first leg adjustment rod 21, a second leg adjustment rod 22, a third leg adjustment rod 23, a fourth leg adjustment rod 24, a fifth leg adjustment rod 25, a sixth leg adjustment rod 26, and a seventh leg adjustment rod 27. In this embodiment, one end of the first leg adjustment rod 21 is hinged to the fourth leg adjustment rod 24, and the first leg adjustment rod 21 is hinged to the second leg adjustment rod 22 at its middle position; the third leg adjustment rod 23 has a first hinge point 231, a second hinge point 232 and a third hinge point 233, and the first hinge point 231, the second hinge point 232 and the third hinge point 233 are not arranged on the same straight line, one end of the second leg adjustment rod 22 is hinged to the first hinge point 231 of the third leg adjustment rod 23, the fourth leg adjustment rod 24 (at its middle position) is hinged to the second hinge point 232 of the third leg adjustment rod 23, and the other end of the fourth leg adjustment rod 24 relative to the first leg adjustment rod 21 is hinged to the sixth leg adjustment rod 26; one end of the fifth leg adjustment rod 25 is hinged to the third hinge point 233 of the third leg adjustment rod 23, and the other end is hinged to the seventh leg adjustment rod 26. The section rod 27 is hinged; the seventh leg adjustment rod 27 is hinged to the mounting plate 11, specifically, one end of the seventh leg adjustment rod 27 is hinged to the third rivet point 1113 of the mounting plate 11, further, one end of the seventh leg adjustment rod 27 is directly hinged to the third rivet point 1113 of the mounting plate 11 through a rivet, and the vertical distance between the third hinge point 1113 and the mounting plane 111 is less than 20mm, 15mm or 13mm; the sixth leg adjustment rod 26 is hinged to the mounting plate 11, specifically, one end of the sixth leg adjustment rod 26 is hinged to the fourth rivet point 1114 of the mounting plate 11, further, one end of the sixth leg adjustment rod 26 is directly hinged to the fourth rivet point 1114 of the mounting plate 11 through a rivet, and the vertical distance between the fourth hinge point 1111 and the mounting plane 111 or the extension line of the mounting plane 111 is less than 10mm,

[0046] Furthermore, a vertical distance between the fourth hinge point 1111 and the mounting plane 111 or an extension line of the mounting plane 111 is less than 1 mm. The middle position of the sixth leg adjustment rod 26 is hinged to the middle position of the fifth leg adjustment rod 25 .

[0047] One end of the linkage adjustment rod 28 in this embodiment is hinged to the third connecting rod 43, and the other end thereof is hinged to the seventh leg adjustment rod 27. When the linkage adjustment rod 28 rotates, the leg unit 2 and the connecting rod structure 4 can be controlled to be linked.

[0048] The driving unit 6 in this embodiment is connected to the control structure 5 and the leg unit 2 respectively. Specifically, the driving unit 2 includes a first bracket 61, a second bracket 62 and a telescopic unit 63, and the two ends of the telescopic unit 63 are respectively connected to the first bracket 61 and the second bracket 62 to adjust the distance between the first bracket 61 and the second bracket 62; the driving unit 6 is connected to the control structure 5, specifically, the first bracket 61 is connected to the first control link 51; the driving unit 6 is connected to the leg adjustment unit 2, specifically, the second bracket 62 is connected to the seventh leg adjustment rod 27. The telescopic unit 63 in this embodiment can be an electric adjustment structure with a cylinder structure, a motor structure, etc. as the main body, so that the telescopic unit 63 can be telescopic.

[0049] The mechanical stretching device in this embodiment has several states when in use to provide different use postures. Specifically, the mechanical stretching device has a sitting state, a leisure state and a lying state.

[0050] like Figures 1 to 3 As shown, the mechanical extension device is in a sitting position. At this time, the leg adjustment unit 2 is in a folded state, and the mounting portion 321 of the first backrest adjustment rod 32 is perpendicular or substantially perpendicular to the mounting plate 11 of the seat unit 1.

[0051] like Figure 4 As shown, the mechanical extension device is in a leisure posture. Compared with the sitting posture, its leg adjustment unit 2 is unfolded to provide support for the legs.

[0052] like Figures 5 to 7 Compared with the leisure posture, the backrest unit 3 is further reclined (the angle between the mounting portion 321 of the first backrest adjustment rod 32 and the mounting plate 11 of the seat unit 1 is increased) so that the user is in a lying position.

[0053] The control principle of the mechanical extension device in this embodiment is as follows: in the sitting state, the drive unit 6 is in the initial state (the first bracket 61 and the second bracket 62 are closest to each other); when the telescopic unit 63 pushes the second bracket 62, and pushes the seventh leg adjustment rod 27 through the second bracket 62, the seventh leg adjustment rod 27 rotates relative to its hinge on the mounting plate 11, and the leg unit 2 is unfolded; when the telescopic unit 63 continues to extend, its first bracket 61 pushes the first control link 51, and the first control link 51 can adjust the angle of the backrest unit 3.

[0054] In the present invention, the connecting rod structure 4 and the control structure 5 are compact in structure and reasonably designed, so that their adjustment operation is smoother and the comfort of use is improved; the structural strength of the backrest unit 3 is improved and it is not easy to be damaged during use; because the vertical distance between the fourth riveted point 1114 and the extension line of the installation plane 111 is not more than 10mm, preferably, the vertical distance between the fourth riveted point 1114 and the extension line of the installation plane 111 is not more than 1mm, which reduces the height of the installation plane and also reduces the thickness of the mechanical stretching device itself.

[0055] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, as long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A mechanical stretching device, characterized in that: include: A seat unit, comprising a mounting plate, a mounting plane being arranged on the mounting plate, and a first riveting point, a second riveting point, a third riveting point and a fourth riveting point being provided on the mounting plate; A connecting rod structure connected to the mounting plate via a first rivet point and a second rivet point on the mounting plate; as well as a leg unit connected to the mounting plate via a third rivet point and a fourth rivet point on the mounting plate; The first riveting point, the second riveting point and the third riveting point are all located below the mounting plane, and the center of the fourth riveting point is located above the mounting plane; and the vertical distance between the center of the fourth riveting point and the extension line of the mounting plane of the mounting plate does not exceed 10 mm; The connecting rod structure comprises a first connecting rod, a second connecting rod and a third connecting rod, wherein one end of the first connecting rod is hinged at a first riveted point of the mounting plate, and the other end thereof is hinged to the third connecting rod; one end of the second connecting rod is hinged at a second riveted point of the mounting plate, and the other end thereof is hinged to the third connecting rod; the first connecting rod, the second connecting rod, the third connecting rod and the mounting plate form a first four-connecting rod structure; Also includes a control structure, the control structure includes a first control link, a second control link, a third control link and a fourth control link; wherein one end of the second control link is hinged to the first control link, and the other end thereof is hinged to the third control link; one end of the fourth control link is hinged to the first control link, and the other end thereof is hinged to the third control link; the first control link, the second control link, the third control link and the fourth control link form a second four-bar linkage structure; The control structure also includes a fifth control link, a sixth control link and a seventh control link; wherein one end of the fifth control link is hinged to the fourth control link, and the other end thereof is hinged to the third link; one end of the sixth control link is hinged to the second control link, and the other end thereof is hinged to the third link; one end of the seventh control link is hinged to one end of the second control link, and the other end thereof is hinged to the third link.

2. The mechanical stretching device according to claim 1, characterized in that: It also includes a backrest unit, which includes a fixed plate, a first backrest adjustment rod, a second backrest adjustment rod, a third backrest adjustment rod and a fourth backrest adjustment rod, wherein the fixed plate is fixed to the mounting plate, one end of the first backrest adjustment rod is hinged to the fixed plate; the third backrest adjustment rod is hinged to the fixed plate and has a first arm and a second arm; one end of the second backrest adjustment rod is hinged to the first backrest adjustment rod, and the other end thereof is hinged to the first arm of the third backrest adjustment rod; the second arm of the third backrest adjustment rod is hinged to the fourth backrest adjustment rod, and the fourth backrest adjustment rod is hinged to the first control link.

3. The mechanical stretching device according to claim 1, characterized in that: The leg unit includes a first leg adjustment rod, a second leg adjustment rod, a third leg adjustment rod, a fourth leg adjustment rod, a fifth leg adjustment rod, a sixth leg adjustment rod, and a seventh leg adjustment rod; one end of the first leg adjustment rod is hinged to the fourth leg adjustment rod, and the first leg adjustment rod is hinged to the second leg adjustment rod at its middle position; the third leg adjustment rod has a first hinge point, a second hinge point and a third hinge point, one end of the second leg adjustment rod is hinged to the first hinge point of the third leg adjustment rod, and the fourth leg adjustment rod is hinged to the third leg adjustment rod The second hinge point of the leg adjustment rod, the other end of the fourth leg adjustment rod relative to the first leg adjustment rod is hinged to the sixth leg adjustment rod; one end of the fifth leg adjustment rod is hinged at the third hinge point of the third leg adjustment rod, and the other end of the fifth leg adjustment rod is hinged to the seventh leg adjustment rod; one end of the seventh leg adjustment rod is hinged to the third rivet point of the mounting plate; one end of the sixth leg adjustment rod is hinged at the fourth rivet point of the mounting plate, and the middle position of the sixth leg adjustment rod is hinged to the middle position of the fifth leg adjustment rod.

4. The mechanical stretching device according to claim 3, characterized in that: The leg unit further comprises a linkage adjustment rod, one end of which is hinged to the third connecting rod, and the other end of which is hinged to the seventh leg adjustment rod.

5. The mechanical stretching device according to claim 3, characterized in that: It also includes a driving unit, which includes a first bracket, a second bracket and a telescopic unit, wherein both ends of the telescopic unit are respectively connected to the first bracket and the second bracket; the first bracket is connected to the first control link; and the second bracket is connected to the seventh leg adjustment rod.

6. The mechanical stretching device according to claim 1, characterized in that: In the sitting state, the intersection of the extension line of the installation plane and the extension line of the outer side of the leg unit is A. When the mechanical extension device is in the sitting state, the distance between the intersection A and the ground is between 255mm and 264mm.

7. The mechanical stretching device according to claim 1, characterized in that: When the mechanical extension device is installed on any one of a sofa, a seat or a wheelchair, and any one of the sofa, the seat or the wheelchair is placed on a horizontal plane, the angle between the installation plane and the horizontal plane is 5 degrees to 10 degrees.

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