Mechanical extension device for a movable seat and movable seat unit

Abstract

The invention relates to a mechanical stretching device for a movable seat. The mechanical stretching device comprises a base unit fixedly supported on the ground; each backrest unit comprises a first backrest connecting rod, a second backrest connecting rod and a backrest mounting plate, and the first backrest connecting rod and the second backrest connecting rod are connected with the base unit in a pivoted mode; two leg stretching units; the linkage connecting rod is connected between the backrest unit and the leg stretching unit; the electric actuator acts between the base unit and the linkage connecting rod, and when the leg stretching unit stretches forwards relative to the base unit, the upper end portion of the first backrest connecting rod and the upper end portion of the second backrest connecting rod pivot backwards at the same time; when the leg extension unit is retracted rearward with respect to the base unit, the upper end of the first backrest link and the upper end of the second backrest link simultaneously pivot forward. The invention also relates to a movable seating unit.

Description

Technical Field

[0001] The present invention relates to a mechanical extension device for a movable seat and a movable seat unit including the mechanical leg extension unit. Background Art

[0002] In the prior art, various movable seats are known, such as sofas or seats with multi-position transformation functions. With the improvement of people's living standards, the requirements for the comfort of sofas and seats are also increasing day by day. In known designs, movable seat units usually have mechanical extension devices, whereby they can be transformed between a sitting position and a lying position. When the seat is transformed from the sitting position to the lying position, the footrest of the seat unit extends forward and the backrest reclines significantly.

[0003] In the existing designs of such seats, there are often a large number of mechanical structures with relatively complex connection relationships, and sometimes the posture transformation of the seat may be stuck due to an unreasonable design. In addition, for some users, the excessive reclining of the backrest does not conform to their living habits. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a mechanical extension device for a movable seat and a corresponding movable seat unit with higher comfort. On the one hand, the seat unit should meet the user's requirements for the backrest adjustment method. On the other hand, during the posture transformation of the movable seat, a smooth and simple posture change should be achieved.

[0005] It should be noted here that in this application, the "front-rear direction" and "front and rear" refer to the extension direction of the seat unit or the leg extension unit of the mechanical extension device. Specifically, the "front" refers to the direction towards the leg extension unit, and the "rear" refers to the direction towards the backrest; the "left-right direction" and "left and right" refer to the left and right hand directions when the user of the seat unit or the mechanical extension device is seated.

[0006] To solve the above technical problems, the present invention provides a mechanical extension device for a movable seat, including:

[0007] A base unit fixedly supported on the ground;

[0008] A backrest unit movably connected to the rear part of the base unit, wherein each backrest unit includes a first backrest link, a second backrest link, and a backrest mounting plate for attaching the backrest, and wherein the first backrest link and the second backrest link are respectively pivotally connected to the base unit;

[0009] Two leg extension units movably connected to the front part of the base unit on the left and right sides;

[0010] A linkage connecting between the backrest unit and the leg extension unit, wherein a front end portion of the linkage is pivotally connected to a transverse link transversely connecting between two leg extension units, and a rear end portion of the linkage is pivotally connected to the backrest unit; and

[0011] An electric actuator acting between the base unit and the linkage, and through a working stroke of the electric actuator, causing telescopic movement of the leg extension unit relative to the base unit to be synchronized with movement of the backrest unit relative to the base unit. Wherein, when the leg extension unit extends forward relative to the base unit, upper end portions of the first backrest link and the second backrest link simultaneously pivot rearward; when the leg extension unit retracts rearward relative to the base unit, upper end portions of the first backrest link and the second backrest link simultaneously pivot forward.

[0012] According to the present invention, one end of the linkage acts on the backrest unit and the other end acts on the leg extension unit. This direct connection of the backrest unit and the leg extension unit through the linkage realizes the linkage between the backrest unit and the leg extension unit. Particularly advantageously, the linkage is also connected to the electric actuator, which enables the power generated by the working stroke of the electric drive to be transmitted to the two leg extension units through the front end portion of the linkage and the transverse link, and at the same time, is transmitted to the backrest unit through the rear end portion of the linkage, without incomplete synchronization of the movement between the backrest unit and the leg extension unit caused by the lag of the movement chain of the mechanical structure. This not only further improves the synchronization of the linkage between the backrest unit and the leg extension unit, but also fully ensures the movement synchronization between the backrest units, realizes a smoother posture transformation process of the mechanical stretching device, and avoids movement jamming.

[0013] Also, due to the linkage relationship between the backrest unit and the leg extension unit, only one electric actuator acting between the leg extension unit and the base unit can complete the synchronous adjustment of the backrest unit and the leg extension unit. This not only reduces parts, simplifies the process, reduces the installation cost and material cost, but also saves the product structure space, realizing the compactness and light weight of the product structure.

[0014] Preferably, upper end portions of the first backrest link and the second backrest link are respectively pivotally connected to the backrest mounting plate, wherein during the extension and retraction of the leg extension unit, the angle change of the backrest mounting plate relative to the horizontal plane is not greater than 15°.

[0015] Particularly preferably, during the extension and retraction of the leg extension unit, the angle of the backrest mounting plate relative to the horizontal plane remains unchanged.

[0016] Particularly preferably, during the extension and retraction of the leg extension unit, the backrest mounting plate remains parallel to the horizontal plane.

[0017] In a preferred embodiment, the first backrest link includes a first pivot point at the middle, a second pivot point at the upper end, and a third pivot point at the lower end. Among them, the first backrest link is pivotally connected to the base unit at the first pivot point, pivotally connected to the backrest mounting plate at the second pivot point, and pivotally connected to the rear end of the linkage link at the third pivot point. The second backrest link includes a fourth pivot point at the upper end and a fifth pivot point at the lower end. Among them, the second backrest link is pivotally connected to the backrest mounting plate at the fourth pivot point and pivotally connected to the base unit at the fifth pivot point. The first pivot point is in front of the fifth pivot point, and the second pivot point is in front of the fourth pivot point. The linear distance between the first pivot point and the second pivot point is equal to the linear distance between the fourth pivot point and the fifth pivot point, and the linear distance between the first pivot point and the fifth pivot point is equal to the linear distance between the second pivot point and the fourth pivot point.

[0018] Thus, the first backrest link, the second backrest link, the base unit pivotally connected thereto, and the backrest mounting plate form a four-bar linkage mechanism of a parallelogram, wherein the backrest mounting plate is located at the upper ends of the first backrest link and the second backrest link. In this case, as the leg extension unit extends and retracts, this four-bar linkage mechanism formed by the backrest unit deforms under the drive of the linkage link. Among them, the backrest mounting plate can basically always face upward during the attitude transformation of the mechanical extension device. This almost constant orientation ensures that the backrest attached to the backrest mounting plate also maintains an almost constant orientation. That is to say, when this four-bar linkage mechanism is stretched and deformed, each point on the backrest mounting plate experiences an arc trajectory that first goes up and then down, which causes the entire backrest mounting plate to translate horizontally without a significant angular change with the horizontal plane. For the user, as the leg extension unit extends, the backrest moves backward without significant reclining.

[0019] According to a preferred embodiment, the base unit includes two side plates facing each other and a leg fixing rod fixedly connected to the side plates, wherein the leg extension unit is pivotally connected to the leg fixing rod.

[0020] As part of the base unit, the shape of the leg fixing rod can be designed as needed. Thus, it can provide a more flexible and larger operating space for the installation of the leg extension unit and simplify the installation process. Appropriate materials can also be used to manufacture the leg fixing rod according to the requirements of strength and hardness to ensure the reliability of the product.

[0021] According to a preferred embodiment, the base unit includes a top plate and a backrest fixing bracket fixedly connected to the top plate, wherein the first backrest link and the second backrest link are respectively pivotally connected to the backrest fixing bracket.

[0022] Also as part of the base unit, the shape of the backrest fixing bracket can be designed as needed, or a suitable material can be used to manufacture the backrest fixing bracket. Thereby, the installation process can be simplified and the reliability of the product can be ensured.

[0023] According to a preferred embodiment, the mechanical extension device includes a front drive rod connected transversely between the linkage links, one end of the electric actuator is connected to the base unit, and the other end is connected to the front drive rod.

[0024] According to a preferred embodiment, the electric actuator includes a linear electric actuator device.

[0025] To solve the above technical problems, the present invention also provides a movable seat unit, at least including:

[0026] An armrest portion, a backrest, and a footrest portion;

[0027] A mechanical extension device, which includes:

[0028] A base unit fixedly supported on the ground, wherein the armrest portion is attached to the base unit;

[0029] A backrest unit movably connected to the rear part of the base unit, wherein each backrest unit includes a first backrest link, a second backrest link, and a backrest mounting plate for attaching the backrest, wherein the first backrest link and the second backrest link are respectively pivotally connected to the base unit;

[0030] Two leg extension units movably connected to the front part of the base unit on the left and right sides;

[0031] Linkage links connected between the backrest unit and the leg extension units, wherein the front end portion of the linkage links is pivotally connected to a transverse link transversely connected between the two leg extension units, and the rear end portion of the linkage links is pivotally connected to the backrest unit; and

[0032] An electric actuator acting between the base unit and the linkage rod causes the telescopic movement of the leg extension unit relative to the base unit and the movement of the backrest unit relative to the base unit to be synchronized through the working stroke of the electric actuator. Wherein, when the leg extension unit extends forward relative to the base unit, the backrest attached to the backrest mounting plate moves backward; when the leg extension unit retracts backward relative to the base unit, the backrest attached to the backrest mounting plate moves forward.

[0033] According to a preferred embodiment, the upper end portions of the first backrest link and the second backrest link are respectively pivotally connected to the backrest mounting plate. Wherein, during the extension and retraction of the leg extension unit, the angle change of the backrest relative to the horizontal plane is not greater than 15°.

[0034] According to a preferred embodiment, during the extension and retraction of the leg extension unit, the angle of the backrest relative to the horizontal plane remains unchanged.

[0035] According to a preferred embodiment, the first backrest link includes a first pivot point in the middle, a second pivot point at the upper end portion, and a third pivot point at the lower end portion. Wherein, the first backrest link is pivotally connected to the base unit at the first pivot point, pivotally connected to the backrest mounting plate at the second pivot point, and pivotally connected to the rear end portion of the linkage rod at the third pivot point.

[0036] According to a preferred embodiment, the second backrest link includes a fourth pivot point at the upper end portion and a fifth pivot point at the lower end portion. Wherein, the second backrest link is pivotally connected to the backrest mounting plate at the fourth pivot point and pivotally connected to the base unit at the fifth pivot point.

[0037] According to a preferred embodiment, the first pivot point is located in front of the fifth pivot point, and the second pivot point is located in front of the fourth pivot point.

[0038] According to a preferred embodiment, the linear distance between the first pivot point and the second pivot point is equal to the linear distance between the fourth pivot point and the fifth pivot point, and the linear distance between the first pivot point and the fifth pivot point is equal to the linear distance between the second pivot point and the fourth pivot point.

[0039] According to a preferred embodiment, the base unit includes two side plates facing each other and a leg fixing rod fixedly connected to the side plates. Wherein, the leg extension unit is pivotally connected to the leg fixing rod.

[0040] According to a preferred embodiment, the base unit includes a top plate and a backrest fixing bracket fixedly connected to the top plate, wherein the first backrest link and the second backrest link are respectively pivotally connected to the backrest fixing bracket.

[0041] According to a preferred embodiment, the mechanical extension device includes a front drive rod connected transversely between the linkage links, and one end of the electric actuator is connected to the base unit and the other end is connected to the front drive rod.

[0042] According to a preferred embodiment, the electric actuator includes a linear electric actuating device.

[0043] The advantages described above for the mechanical extension device also apply equally to the movable seat unit having such a mechanical extension device. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0045] Figure 1 A mechanical extension device for a movable seat according to an embodiment of the present invention is schematically shown in a perspective view in a sitting position;

[0046] Figure 2 Shown Figure 2 The mechanical extension device shown in a lying position;

[0047] Figure 3 Shown in a perspective view Figure 1 Some components of the mechanical extension device shown in a sitting position;

[0048] Figure 4 Shown in a perspective view Figure 1 Some components of the mechanical extension device shown in a lying position;

[0049] Figure 5 Schematically shown in a side view Figure 1 The sitting position of the mechanical extension device shown;

[0050] Figure 6 Schematically shown in a side view Figure 1 The lying position of the mechanical extension device shown; and

[0051] Figure 7 Schematic diagrams of the mechanical extension device with a backrest in the sitting position and the lying position are shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] As used herein, the term "one embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Moreover, the terms "first", "second", etc. are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0054] Figure 1 and Figure 2 The mechanical extension device 100 of the movable seat according to the present invention is shown in a perspective view, which includes a multi-link mechanism and is configured such that the movable seat can be transformed between a sitting position and a lying position.

[0055] As Figure 1 shown, the mechanical extension device 100 is configured for an armrest floor-standing movable seat and includes a base unit 1 fixedly supported on the ground, and mechanical extension device halves symmetrically arranged on the left and right sides, wherein each mechanical extension device half respectively includes a backrest unit 2 and a leg extension unit 3.

[0056] The base unit 1 is constructed in a frame shape and includes two side plates 12 longitudinally extending along the front-back direction of the movable seat, a rear plate 14 fixedly connected between the two side plates 12 in the transverse direction and perpendicular to the horizontal plane, a top plate 15 fixedly connected to the side plates 12 and parallel to the horizontal plane, and a base cross beam 16 located in front of the top plate 15 and fixedly connected to the side plates 12. A slot corresponding to the backrest unit 2 is provided on the top plate 15 of the base unit 1 to provide necessary movement space for the backrest unit 2. The front part of the base unit 1 is open to allow the leg extension unit 3 to extend forward.

[0057] The backrest units 2 are respectively movably connected to the rear part of the base unit 1. Each backrest unit 2 includes a first backrest link 21, a second backrest link 22, and a backrest mounting plate 23 for attaching the backrest. The base unit 1 includes a backrest fixing bracket 20 designed for mounting the backrest unit 2. The backrest fixing bracket 20 includes a horizontal section 20a fixedly connected to the top plate 15 and a vertical section 20b fixedly connected perpendicularly to the horizontal section 20a. Two perforations are provided on the vertical section 20b for pivotally connecting to the first backrest link 21 and the second backrest link 22. Every two backrest fixing brackets 20 are arranged in a pair facing each other to pivotally connect the first backrest link 21 and the second backrest link 22 to the base unit 1.

[0058] The first backrest link 21 includes three pivot points, namely a first pivot point P1 located at its middle part, a second pivot point P2 located at its upper end part, and a third pivot point P3 located at its lower end part. The second backrest link 22 includes two pivot points, namely a fourth pivot point P4 located at its upper part and a fifth pivot point P5 located at its lower end part. The first backrest link 21 is located in front of the second backrest link 22 in the front-back direction of the seat unit. The backrest mounting plate 23 is oriented upward and is substantially parallel to the horizontal plane. The bottom side of the backrest mounting plate 23 is provided with mounting flanges for pivotally connecting with the first backrest link 21 and the second backrest link 22. Specifically, the first backrest link 21 is pivotally connected to the backrest fixing bracket 20 of the base unit 1 at the first pivot point P1 and is pivotally connected to the backrest mounting plate 23 at the second pivot point P2. The second backrest link 22 is pivotally connected to the backrest mounting plate 23 at the fourth pivot point P4 and is pivotally connected to the backrest fixing bracket 20 of the base unit 1 at the fifth pivot point P5. Here, the linear distance between the first pivot point P1 and the second pivot point P2 is approximately equal to the linear distance between the fourth pivot point P4 and the fifth pivot point P5, and the linear distance between the first pivot point P1 and the fifth pivot point P5 is approximately equal to the linear distance between the second pivot point P2 and the fourth pivot point P4. Thus, the first backrest link 21, the second backrest link 11, the backrest fixing bracket 20, and the backrest mounting plate 23 form a four-bar linkage of a parallelogram. When the first backrest link 21 and the second backrest link 22 pivot around their respective pivot points with the base unit 1, the backrest mounting plate 23 is correspondingly driven to translate forward or backward. During this process, the angle between the backrest mounting plate 23 and the horizontal plane always remains unchanged. In this embodiment, the backrest mounting plate 23 extends parallel to the horizontal plane, and during the attitude transformation process of the backrest unit 2, the backrest mounting plate 23 always maintains an orientation substantially parallel to the horizontal plane.

[0059] Two leg extension units 3 are respectively movably connected to the front part of the base unit 1. Each leg extension unit 3 includes a first leg link 31, a second leg link 32, a third leg link 33, a fourth leg link 34 and a footrest mounting plate 35. The base unit 1 includes a leg fixing rod 30 designed for mounting the leg extension unit 3. The rear end of the leg fixing rod 30 is fixedly connected to the side plate 12 of the base unit 1, and its front part bends inward to provide an operating space for the installation of the leg extension unit 3. The rear end of the first leg link 31 is pivotally connected to the leg fixing rod 30, and its front end is pivotally connected to the rear end of the third leg link 32. The rear end of the second leg link 32 is pivotally connected to the leg fixing rod 30, and its front end is pivotally connected to the rear end of the fourth leg link 34. The front ends of the third leg link 33 and the fourth leg link 34 are respectively pivotally connected to the footrest mounting plate 35. The pivot point of the first leg link 32 and the leg fixing rod 30 is located behind the pivot point of the second leg link 32 and the leg fixing rod 30. The second leg link 32 is pivotally connected to the third backrest link 33. The leg extension unit 3 can be in the retracted position as shown in Figure 1 , Figure 3 , Figure 5 and the deployed position as shown in Figure 2 , Figure 4 , Figure 6 . To ensure the synchronous movement between the leg extension units 3, a lateral link 36 is connected between the two leg extension units 3.

[0060] The mechanical stretching device 1 further includes a linkage link 4 connected between the backrest unit 2 and the leg extension unit 3. The rear end part of the linkage link 4 is configured as a tab 40 with a perforation, so that the linkage link 4 is pivotally connected to the third pivot point P3 at the lower end of the first backrest link 21 with its rear end part; the lateral link 36 includes a bracket 37 with a perforation, and the linkage link 4 is pivotally connected to the bracket 37 with its front end part. The direct connection of the linkage link 4 to the backrest unit 2 and the leg extension unit 3 realizes the linkage between the backrest unit 2 and the leg extension unit 3.

[0061] The mechanical stretching device 100 further includes an electric actuator 5 acting between the base unit 1 and the linkage link 4. The electric actuator 5 is configured as a linear electric actuating device herein, and the linear electric actuating device includes a motor head 51 and a motor push rod 52 that is telescopic relative to the motor head 51. The motor head 51 is fixedly installed relative to the base unit 1. For the sake of simplicity, in the embodiments as shown in Figure 3 and Figure 4 , the side plate 12, the rear plate 14, the top plate 15 and the base cross beam 16 of the base unit 1 are hidden. The bottom side of the top plate 15 of the base unit 1 is fixedly installed with Figure 3The L-shaped fixing member 25 shown and the motor cross beam 26 connected between the L-shaped fixing members 25, wherein the motor cross beam 26 is located behind the transverse link 36. The motor head 51 is pivotally connected to the motor head bracket fixedly connected to the motor cross beam 51, so as to mount the motor head 51 at the rear of the base unit 1. Here, during the transformation of the seat unit from the sitting position to the lying position, the motor head has no movement component in the front-rear direction, but can pivot around an axis transverse to the front-rear direction. The motor push rod 52 acts on the front drive rod 42 transversely connected between the two linkage rods 4. Of course, in an embodiment not shown, the positions of the motor head 51 and the motor push rod 52 can also be reversed.

[0062] If the seat unit is to move from Figure 1 , Figure 3 and Figure 5 the sitting position shown to Figure 2 , Figure 4 and Figure 6 the lying position shown in 2, the motor push rod 52 of the electric drive 5 extends relative to the motor head 51, and the resulting power is synchronously transmitted to the leg extension unit 3 and the backrest unit 2 respectively through the front drive rod 42 and the linkage rod 4 rigidly connected thereto. In this case, as the pair of linkage rods 4 moves forward, the second link 32 of the leg extension unit 3 moves forward, thereby promoting the leg extension unit 3 to unfold relative to the base unit 1. At the same time, the lower end of the first backrest link 21 pivotally connected to the linkage rod 4 pivots forward around the first pivot point P1, and promotes the entire backrest unit 2 to pivot. Here, the upper ends of the first backrest link 21 and the second backrest link 2 pivot backward around the first pivot point P1 and the second pivot point P2 fixed relative to the base unit respectively, and the backrest fixing plate 23 moves backward.

[0063] If the seat unit is to move from Figure 2 , Figure 4 and Figure 6 the lying position shown in 2 to Figure 1 , Figure 3 and Figure 5In the sitting position shown, the motor push rod 52 of the electric drive 5 is retracted relative to the motor head 51, and the power generated thereby is synchronously transmitted to the leg extension unit 3 and the backrest unit 2 respectively through the front drive rod 42 and the linkage link 4 rigidly connected thereto. In this case, as the linkage link 4 moves backward, the second link 32 of the leg extension unit 3 moves backward, thereby causing the leg extension unit 3 to be retracted relative to the base unit 1. At the same time, the lower end of the first backrest link 21 pivotally connected to the linkage link 4 pivots backward around the first pivot point P1, and causes the entire backrest unit 2 to pivot. Here, the upper ends of the first backrest link 21 and the second backrest link 2 pivot forward around the first pivot point P1 and the second pivot point P2, respectively, and the backrest fixing plate 23 moves forward.

[0064] That is, once the leg extension unit 3 is extended or retracted relative to the base unit 1 , the backrest fixing plate 23 of the backrest unit 2 is simultaneously moved backward or forward relative to the base unit 1 .

[0065] Figure 5 and Figure 6 A side view of the mechanical extension device in a sitting position and a lying position is shown respectively. Figure 5 In the sitting position shown, the leg extension unit 3 is folded relative to the base unit 1 and the backrest mounting plate 23 is substantially parallel to the horizontal plane. Figure 6 In the lying position shown, the leg extension unit 3 is extended forward relative to the base unit 1, and the backrest mounting plate 23 remains substantially parallel to the horizontal plane, but moves backward relative to the sitting position. In this process, since the upper ends of the first backrest link 21 and the second backrest link 22 respectively experience arc trajectories around the first pivot point P1 and the second pivot point P2, the backrest mounting plate 23 also changes in height accordingly. The height difference H between the backrest mounting plate 23 and the top plate 15 can experience a process of first rising and then falling. In this embodiment, the height difference can be changed from about 160 mm to 220 mm, and then reduced to 160 mm.

[0066] Accordingly, Figure 7 A mechanical extension device 100 is shown with a schematic backrest. The backrest 200 is attached to a backrest mounting plate 23. Figure 7 In the sitting position shown above, the leg extension unit 3 is folded up. Figure 7 In the lying position shown below, the leg extension unit 3 is folded relative to the base unit 1. Since the backrest mounting plate 23 always remains horizontal during the change between the sitting position and the lying position, the angle of the backrest 200 relative to the horizontal plane remains unchanged and only moves forward and backward relative to the base unit 1.

Claims

1. A mechanical extension device for a movable seat, comprising: A base unit fixedly supported on the ground; A backrest unit movably connected to the rear of the base unit, wherein each backrest unit includes a first backrest link, a second backrest link, and a backrest mounting plate for attaching the backrest, wherein the first backrest link and the second backrest link are respectively pivotally connected to the base unit; Two leg extension units movably connected to the front of the base unit on the left and right sides; A linkage connecting between the backrest unit and the leg extension units, wherein the front end of the linkage is pivotally connected to a transverse link horizontally connecting between the two leg extension units, and the rear end of the linkage is pivotally connected to the backrest unit; and An electric actuator acting between the base unit and the linkage, causing the telescopic movement of the leg extension units relative to the base unit to be synchronized with the movement of the backrest unit relative to the base unit through the working stroke of the electric actuator, wherein when the leg extension units extend forward relative to the base unit, the upper ends of the first backrest link and the second backrest link pivot backward simultaneously; when the leg extension units retract backward relative to the base unit, the upper ends of the first backrest link and the second backrest link pivot forward simultaneously.

2. The mechanical stretching device according to claim 1, wherein The upper ends of the first backrest link and the second backrest link are respectively pivotally connected to the backrest mounting plate, wherein during the extension and retraction of the leg extension units, the angle change of the backrest mounting plate relative to the horizontal plane is not greater than 15°.

3. The mechanical extension device according to claim 2, characterized in that, During the extension and retraction of the leg extension units, the angle of the backrest mounting plate relative to the horizontal plane remains unchanged.

4. The mechanical extension device according to claim 3, characterized in that During the extension and retraction of the leg extension units, the backrest mounting plate remains parallel to the horizontal plane.

5. The mechanical extension device according to claim 2, wherein The first backrest link includes a first pivot point in the middle, a second pivot point at the upper end, and a third pivot point at the lower end, wherein the first backrest link is pivotally connected to the base unit at the first pivot point, pivotally connected to the backrest mounting plate at the second pivot point, and pivotally connected to the rear end of the linkage at the third pivot point.

6. The mechanical stretching device according to claim 5, wherein The second backrest link includes a fourth pivot point at the upper end and a fifth pivot point at the lower end, wherein the second backrest link is pivotally connected to the backrest mounting plate at the fourth pivot point and pivotally connected to the base unit at the fifth pivot point.

7. The mechanical stretching device according to claim 6, wherein The first pivot point is located in front of the fifth pivot point, and the second pivot point is located in front of the fourth pivot point.

8. The mechanical stretching device according to claim 6, characterized in that The straight-line distance between the first pivot point and the second pivot point is equal to the straight-line distance between the fourth pivot point and the fifth pivot point, and the straight-line distance between the first pivot point and the fifth pivot point is equal to the straight-line distance between the second pivot point and the fourth pivot point.

9. The mechanical stretching device according to claim 1, characterized in that, The base unit includes two side plates facing each other and leg fixing rods fixedly connected to the side plates, wherein the leg extension units are pivotally connected to the leg fixing rods.

10. The mechanical stretching device according to claim 1, characterized in that, The base unit includes a top plate and a backrest fixing bracket fixedly connected to the top plate. Among them, the first backrest link and the second backrest link are respectively pivotally connected to the backrest fixing bracket.

11. The mechanical extension device according to claim 1, characterized in that, The mechanical extension device includes a front drive rod transversely connected between the linkage links. One end of the electric actuator is connected to the base unit, and the other end is connected to the front drive rod.

12. The mechanical extension device according to claim 1, wherein, The electric actuator includes a linear electric actuating device.

13. A movable seat unit, at least including: An armrest portion; A backrest; A footrest; A mechanical extension device (100), which includes: A base unit fixedly supported on the ground, wherein the armrest portion is attached to the base unit; A backrest unit movably connected to the rear part of the base unit. Each backrest unit includes a first backrest link, a second backrest link, and a backrest mounting plate for attaching the backrest. Among them, the first backrest link and the second backrest link are respectively pivotally connected to the base unit; Two leg extension units movably connected to the front part of the base unit on the left and right sides, and the footrest is attached to the leg extension units; Linkage links connected between the backrest unit and the leg extension units. The front end portion of the linkage link is pivotally connected to a transverse link transversely connected between the two leg extension units, and the rear end portion of the linkage link is pivotally connected to the backrest unit; and An electric actuator acting between the base unit and the linkage link, through the working stroke of the electric actuator, causing the telescopic movement of the leg extension units relative to the base unit to be synchronized with the movement of the backrest unit relative to the base unit. Among them, when the leg extension units extend forward relative to the base unit, the backrest attached to the backrest mounting plate moves backward; when the leg extension units retract backward relative to the base unit, the backrest attached to the backrest mounting plate moves forward.

14. The movable seat unit according to claim 13, wherein, The upper end portions of the first backrest link and the second backrest link are respectively pivotally connected to the backrest mounting plate. Among them, during the extension and retraction of the leg extension units, the angle change of the backrest relative to the horizontal plane is not greater than 15°.

15. The movable seat unit according to claim 14, characterized in that, During the extension and retraction of the leg extension units, the angle of the backrest relative to the horizontal plane remains unchanged.

16. The movable seat unit according to claim 14, characterized in that, The first backrest link includes a first pivot point in the middle, a second pivot point at the upper end portion, and a third pivot point at the lower end portion. Among them, the first backrest link is pivotally connected to the base unit at the first pivot point, pivotally connected to the backrest mounting plate at the second pivot point, and pivotally connected to the rear end portion of the linkage link at the third pivot point.

17. The movable seat unit according to claim 16, characterized in that, The second backrest link includes a fourth pivot point at the upper end portion and a fifth pivot point at the lower end portion. Among them, the second backrest link is pivotally connected to the backrest mounting plate at the fourth pivot point and pivotally connected to the base unit at the fifth pivot point.

18. The movable seat unit according to claim 17, characterized in that, The first pivot point is in front of the fifth pivot point, and the second pivot point is in front of the fourth pivot point.

19. The movable seat unit according to claim 17, wherein, The linear distance between the first pivot point and the second pivot point is equal to the linear distance between the fourth pivot point and the fifth pivot point, and the linear distance between the first pivot point and the fifth pivot point is equal to the linear distance between the second pivot point and the fourth pivot point.

20. The movable seat unit according to claim 13, characterized in that, The base unit includes two side plates facing each other and a leg fixing rod fixedly connected to the side plates, wherein the leg extension unit is pivotally connected to the leg fixing rod.

21. The movable seat unit according to claim 13, characterized in that, The base unit includes a top plate and a backrest fixing bracket fixedly connected to the top plate, wherein the first backrest link and the second backrest link are respectively pivotally connected to the backrest fixing bracket.

22. The movable seat unit according to claim 13, characterized in that, The mechanical extension device includes a front drive rod connected transversely between the linkage links, and one end of the electric actuator is connected to the base unit and the other end is connected to the front drive rod.

23. The movable seat unit according to claim 13, characterized in that, The electric actuator includes a linear electric actuator device.

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