Mechanical extension device for movable seat unit, and seat unit

Abstract

A mechanical extension device for a movable seat unit, the mechanical extension device comprising: a base assembly (11); a side plate (140) configured to be attached to a seat portion (500) of the seat unit; a backrest assembly (2), comprising a backrest mounting member (20) and a backrest linkage assembly, wherein the backrest linkage assembly comprises a first backrest link (21) and a second backrest link (22), an upper end portion of the first backrest link (21) and a front end of the backrest mounting member (20) being hinged at a first pivot point (P1), a front end portion of the second backrest link (22) and the side plate (140) being hinged at a second pivot point (P2), and a middle portion of the second backrest link (22) being hinged to a middle portion of the first backrest link (21); a central linkage member (15); and a leg extension device (3). The mechanical extension device enables the seat unit to be shifted between at least a sitting position and a lying position. Compared to the sitting position, the lying position has a smaller distance between the first pivot point (P1) and the second pivot point (P2). Further provided is a movable seat unit.

Description

Mechanical extension device for a movable seating unit and seating unit TECHNICAL FIELD

[0001] The present application relates to a mechanical extension device for a movable seating unit and to a seating unit comprising said mechanical extension device. BACKGROUND

[0002] Various movable seating units, such as sofas or chairs with multi-position conversion function, are known in the art. With the improvement of people's living standards, the comfort requirements for sofas and chairs are also increasing. In the known designs, the movable seating units are usually provided with a mechanical extension device, by means of which the seating unit can be converted between a sitting position, a TV position (or a leisure position) and a lying position. When the seating unit is converted from the sitting position to the TV position, the ottoman of the seating unit is extended forward, and the angle between the backrest and the seat part remains substantially unchanged. When the seating unit is converted from the leisure position to the lying position, the ottoman is further extended forward and lifted upward compared to the leisure position, and the backrest is significantly reclined, so that the user of the seating unit is in a lying position with the legs higher than the head, experiencing the so-called "zero gravity" feeling.

[0003] However, the disadvantage in the known designs is that, with the conversion of the seating unit to the lying position, a gap appears between the backrest part and the seat part, which on the one hand pulls the user's upper garment upward, and on the other hand leads to the risk of articles falling from the gap. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a seating unit with simple structure and more in line with human engineering mechanics.

[0005] To solve the above technical problem, the present application provides a mechanical extension device for a movable seating unit, comprising:

[0006] a base assembly supported fixedly on the ground;

[0007] a side plate movably supported above the base assembly, for attaching a seat part of the seating unit;

[0008] a backrest assembly pivotally connected to the rear part of the side plate, comprising a backrest mounting member and a backrest link assembly; and

[0009] a central link movably connected between the side plate and the backrest assembly;

[0010] The backrest linkage assembly comprises a first backrest linkage and a second backrest linkage, the upper end of the first backrest linkage is hingedly connected to the front end of the backrest mounting at a first pivot point, the front end of the second backrest linkage is hingedly connected to the side plate at a second pivot point, and the middle part of the second backrest linkage is hingedly connected to the middle part of the first backrest linkage;

[0011] a leg stretching device pivotally connected to the front part of the side plate, comprising a plurality of linkages pivotally connected to each other, and a first footrest for attaching a footstool;

[0012] The mechanical stretching device enables the seat unit to be transformed between at least a sitting position and a lying position, in the sitting position, the first footrest is retracted below the seat part; in the lying position, the backrest is inclined backward, and the first footrest is extended forward compared with the sitting position, and wherein the distance between the first pivot point and the second pivot point is reduced in the lying position compared with the sitting position.

[0013] In some embodiments, the backrest linkage assembly is compressed and expanded by the relative movement between the central linkage and the side plate, so as to realize the rotation of the backrest mounting around the first pivot point backward and forward.

[0014] In some embodiments, the backrest linkage assembly further comprises a third backrest linkage, wherein the lower end of the first backrest linkage is hingedly connected to the central linkage at a third pivot point, the upper end of the third backrest linkage is hingedly connected to the rear end of the backrest mounting, and the lower end of the third backrest linkage is hingedly connected to the rear end of the second backrest linkage.

[0015] In some embodiments, during the transformation of the seat unit from the sitting position to the lying position, the relative movement between the side plate and the central linkage causes the distance between the second pivot point and the third pivot point to increase, so as to realize the compression of the backrest linkage assembly.

[0016] According to the present application, the backrest mounting is coupled with the seat assembly through the backrest linkage assembly. Through the scissors structure of the backrest linkage assembly, while the backrest mounting rotates backward, the backrest linkage assembly itself is compressed and moves as a whole toward the front of the seat unit relative to the ground. Thus, the gap that may occur between the backrest and the seat part during the posture transformation of the seat unit is reduced or even eliminated. This not only realizes a truly "zero wall" structure, saves installation space, but also reduces or even eliminates the risk of falling of articles due to the above-mentioned gap, avoids the clothes of the user being pulled out, and realizes the comfortable experience of "zero back rubbing".

[0017] In some embodiments, the leg stretching device further comprises a second footrest, in the sitting position, both the first footrest and the second footrest are retracted under the seat part; in the lying position, the backrest is reclined backward, the highest point of the footstool is higher than the highest point of the backrest, wherein both the first footrest and the second footrest are extended forward and upward, and the second footrest is in front of the first footrest.

[0018] In some embodiments, the first footrest and the second footrest are connected by a footrest extension assembly, the footrest extension assembly comprises a first extension and a second extension which are hingedly connected to each other.

[0019] In some embodiments, one end of the first extension is hingedly connected to the second footrest at the distal end, the other end of the second extension is hingedly connected to one end of the second extension, and the other end of the second extension is hingedly connected to the leg link connecting the first footrest at the proximal end, by adjusting the hinged position of the first extension and the second footrest, the front end of the second footrest is raised or lowered in the lying position, so that the corresponding footrest surface forms an angle with the horizontal plane which is comfortable for the user.

[0020] In some embodiments, the seat part assembly further comprises a front swing rod, a rear swing rod, a seat part link and a side plate link, wherein the lower ends of the front swing rod and the rear swing rod are respectively pivotally connected to the base assembly, and the upper ends of the front swing rod and the rear swing rod are connected to the side plate through the central link, the seat part link and the side plate link.

[0021] In some embodiments, the movement of the backrest assembly and the leg stretching device relative to the seat part assembly is facilitated by the swing of the side plate relative to the base assembly, so as to realize the transformation of the seat unit between the sitting position and the lying position.

[0022] In some embodiments, in the lying position, the highest point of the first footrest is higher than the highest point of the backrest mounting. Thereby, a zero-gravity posture is achieved, improving the comfort of the user.

[0023] In some embodiments, the mechanical stretching device further comprises an electric drive device coupled between the base assembly and the side plate.

[0024] To solve the above technical problems, the application also provides a seat unit, which comprises the above mechanical stretching device and a frame assembly connected to the mechanical stretching device, the frame assembly comprises:

[0025] a seat part frame fixedly attached to the side plate and used to support the seat part of the seat unit;

[0026] an armrest frame fixedly attached to both sides of the seat part frame;

[0027] -a backrest frame fixedly attached to the backrest mount and serving to support a backrest of the seat unit. BRIEF DESCRIPTION OF DRAWINGS

[0028] Embodiments of the present application will be described in detail below with reference to the attached drawings.

[0029] Fig. 1 shows a perspective view of a mechanical stretch device together with a frame assembly in a sitting position according to an embodiment of the present application;

[0030] Fig. 2 shows a perspective view of a mechanical stretch device in a sitting position according to an embodiment of the present application;

[0031] Fig. 3 shows a side view of the mechanical stretch device shown in Fig. 2;

[0032] Fig. 4 shows a partial side view of the mechanical stretch device shown in Fig. 2, viewed from another direction;

[0033] Fig. 5 shows a side view of a seat unit in a sitting position according to an embodiment of the present application;

[0034] Fig. 6 shows a side view of the seat unit shown in Fig. 5 in a TV position;

[0035] Fig. 7 shows a side view of the seat unit shown in Fig. 5 in a lying position;

[0036] Fig. 8 shows a side view of a seat unit in a sitting position according to an embodiment of the present application;

[0037] Fig. 9 shows a side view of the seat unit shown in Fig. 8 in a TV position; and

[0038] Fig. 10 shows a side view of the seat unit shown in Fig. 8 in a lying position. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0040] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "left," "right," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0041] Unless otherwise stated, the terms "front" or "front of the seat unit" or "front of the mechanical extension device" as used herein refer to the direction toward the leg extension device with respect to the seat unit; correspondingly, the terms "rear" or "rear of the seat unit" or "rear of the mechanical extension device" as used herein refer to the direction toward the backrest assembly with respect to the seat unit.

[0042] First, a perspective view of a movable seat unit is schematically shown according to Figure 1.

[0043] The seat unit includes a mechanical extension device and a frame assembly attached thereto. The frame assembly includes a seat frame 50, armrest frames 51 fixedly connected to the seat frame 50 on both sides, and a backrest frame 52 movable relative to the seat frame 50. The seat frame 50 is generally constructed as a frame with a rectangular cross-section and is used to support the seat portion 500 as shown in Figures 5 to 7. In some embodiments, the seat portion is elastically constructed, and in some embodiments, it is constructed as a resilient cushion. The backrest frame 52 may be constructed as two mirror-symmetrical plate-like members as shown in Figure 1; however, in embodiments not shown, it may also be constructed as a single plate-like member extending between the two armrest frames 51. The backrest frame 52 is constructed to support the backrest 520 as shown in Figures 5 to 7. In some embodiments, the backrest 520 is elastically constructed, and in some embodiments, it is constructed as a resilient cushion.

[0044] The mechanical extension device as shown in Fig. 2 comprises a seat assembly 1, a backrest assembly 2 and a leg extension device 3. The backrest assembly 2 is hingedly connected to the rear of the seat assembly 1, and the leg extension device 3 is hingedly connected to the front of the seat assembly 1. The seat assembly 1 is attached to the seat portion 520 of a seat unit, the backrest assembly 2 is attached to the backrest portion 520 of the seat unit, and the leg extension device 3 is attached to a footrest of the seat unit, not shown.

[0045] By relative movement of the seat assembly 1, the backrest assembly 2 and the leg extension device 3, the seat unit, or rather its mechanical extension device, can be transformed between a sitting position, a TV position and / or a lying position. In the sitting position, the backrest 520 is upright, and the footrest is retracted under the seat portion 500. In the TV position, the backrest 520 is not significantly inclined backwards, and the footrest is moved upwards and forwards to the front of the seat portion 500 with the extension of the leg extension device 3. In the lying position, the footrest remains extended to the front of the seat portion 500, while the backrest 520 is significantly inclined backwards.

[0046] The seat assembly 1 comprises a base assembly 11, a front swing lever 12, a rear swing lever 13 and a side plate 140.

[0047] In the embodiment as shown in Fig. 1, the mechanical extension device is used for a floor stand type seat unit, and the base assembly 11 directly supports the mechanical extension device on the floor surface and comprises two mirror-symmetrical base longitudinal beams 111 arranged on the left and right sides, and a base front cross beam 112 and a base rear cross beam 113 connecting the two base longitudinal beams 111. However, in an embodiment not shown, the base assembly 11 can also indirectly support the mechanical extension device above the floor surface, for example, the base assembly 11 is rotatably mounted on a rotating base, or the base assembly 11 is fixedly coupled to an armrest portion of an armrest floor stand type seat unit.

[0048] The front swing lever 112 is hingedly connected to the front end of the base longitudinal beam 111 with its lower end, and the rear swing lever 113 is hingedly connected to the rear end of the base longitudinal beam 111 with its lower end.

[0049] The side plate 140 comprises a front support section 140a and a rear support section 140b at its upper portion, which are configured as sections that are horizontally bent inwards or outwards from the side plate 140, and are used to support an auxiliary seat portion frame 50a, wherein a seat portion frame 50 is fixedly connected to the auxiliary seat portion frame 50a.

[0050] The side plate 140 can move relative to the base assembly 11, and also relative to the ground. To this end, as shown in Figs. 3 and 4, the mechanical extension device further comprises a central linkage 15, a seat portion linkage 16 and a side plate linkage 17.

[0051] The central link 15 is provided with a plurality of pivot points, at which the central link 15 is respectively hinged with the backrest assembly 2, with the side plate 140, with the seat portion link 16 and with the rear swing lever 13. One end of the seat portion link 16 is hinged with the front swing lever 12 through the side plate link 17, and the other end of the seat portion link 16 is hinged with the central link 15. Thus, the swing of the front swing lever 12 and the rear swing lever 13 can drive the movement of the side plate 140 relative to the base assembly 11, and further drive the movement of the backrest assembly 2.

[0052] The backrest assembly 2 comprises a backrest mounting 20 attached with a backrest 520, and a backrest link assembly pivotally connected with the backrest mounting 20. The backrest mounting 20 is fixedly connected with a lower section of a backrest frame 52, and the backrest 520 is firmly supported on the backrest frame 52. The backrest link assembly comprises a first backrest link 21, a second backrest link 22 and a third backrest link 23. An upper end of the first backrest link 21 is hinged with a front end of the backrest mounting 20 at a first pivot point P1, a front end of the second backrest link 22 is hinged with the side plate 140 at a second pivot point P2, a rear end of the second backrest link 22 is hinged with a lower end of the third backrest link 23, a middle portion of the second backrest link 22 is hinged with the first backrest link 21, an upper end of the third backrest link 23 is hinged with a rear end of the backrest mounting 20, and a lower end of the first backrest link 21 is hinged with the central link 15 at a third pivot point P3.

[0053] As shown in FIG. 6 in particular, the leg stretching device 3 is composed of a plurality of links pivotally connected with each other, wherein a rear end of a first leg link 31 is hinged with the side plate 140, a front end of the first leg link 31 is hinged with a rear end of a second leg link 32, a rear end of a third leg link 33 is hinged with a front end of the side plate 140, a front end of the third leg link 33 is hinged with a rear end of a fourth leg link 34, and a front end of the second leg link 32 and a front end of the fourth leg link 34 are respectively hinged with a first footrest 35.

[0054] In addition, the mechanical stretching device further comprises a first transmission 18 and a second transmission 19 pivotally connected with each other, one end of the first transmission 18 is hinged with one end of the second transmission 19, the other end of the first transmission 18 is hinged on the side plate 140, and the other end of the second transmission 19 is hinged to the leg stretching device 3, in particular hinged with the first leg link 31. Thus, when the side plate 140 of the seat assembly 1 moves relative to the base assembly 11, the contraction and extension movement of the leg stretching device 3 is driven.

[0055] To enable the seat unit to be transformed between different positions, an electric drive 4 is also provided. The side plate 140 comprises a motor crossbar 40 fixedly connected on its inner side, and the electric drive 4 is coupled between the motor crossbar 40 and the base front crossbeam 112 of the base assembly 11. In some embodiments, the drive 4 is designed as a linear electric drive, by the telescopic movement of which the side plate 140 can be moved relative to the base assembly 11, thereby bringing about movement of the backrest assembly 2 and the leg stretching device 3, so as to realize transformation of the seat unit between different positions, such as a sitting position, a TV position and / or a lying position.

[0056] The electric drive 4 is designed in the present embodiment to facilitate transformation of the mechanical stretching device of the seat unit between the sitting position, the TV position and the lying position. The electric drive 4 comprises a motor head 41, a motor slide rail 42 fixedly connected with the motor head 41, a motor slide block 43 slidable along the motor slide rail 42 relative to the motor head 41, and a motor connecting rod 44. The motor head 41 is fixedly installed on the base front crossbeam 112, and the motor connecting rod 44 is hingedly connected at one end to the motor slide block 43 and at the other end to the motor crossbar 40.

[0057] The mechanical stretching device further comprises a first linkage 141, a second linkage 142 and a third linkage 143. The middle part of the second linkage 142 is rotatably connected with the side plate 140, one end of the second linkage 142 is connected with one end of the first linkage 141, the other end of the first linkage 141 is connected with the front swing lever 12, the other end of the second linkage 142 is connected with one end of the third linkage 143, and the other end of the third linkage 143 is pivotally connected with the first leg connecting rod 31 of the leg stretching device 3.

[0058] Figures 5 to 7 schematically show side views of the seat unit in the sitting position, the TV position and the lying position. For the sake of clarity, the seat part frame and one side armrest frame of the frame assembly of the seat unit are omitted.

[0059] Figures 8 to 10 also schematically show side views of the seat unit in the sitting position, the TV position and the lying position. Again for the sake of clarity, the seat part, the backrest part and one side armrest frame of the frame assembly of the seat unit are omitted.

[0060] When the mechanical stretching device is in the sitting position shown in Figure 5 or Figure 8, the backrest mounting 20 and the backrest 520 of the backrest assembly 2 are upright, and the leg stretching device 3 is retracted below the seat part 500.

[0061] In the process of transforming the mechanical stretching device from the sitting position shown in Fig. 5 or Fig. 8 to the TV position shown in Fig. 6 or Fig. 9, the electric drive device 4 is operated so that the motor slider 43 slides along the motor rail 42 towards the motor head 41, so that the distance between the motor head 41 and the motor slider 43 is reduced. In this process, the motor slider 43 moves the side plate 140 forward, i.e. in the direction of the leg stretching device 3, through the motor link 44, and the front swing lever 12 and the rear swing lever 13 swing forward accordingly. Thus, the first linkage 141 moves forward with the front swing lever 12 and pushes the first leg link 31 with the second linkage 142 and the third linkage 143; and further causes the leg stretching device 3 to unfold. The side plate linkage 17 and the seat linkage 16 also move forward with the front swing lever 12 and move the central linkage 15 forward. In this process, the central linkage 15 moves forward together with the side plate 140, and further moves the backrest assembly 2 as a whole forward and downward with the first backrest link 21 and the second backrest link 22, while the backrest mounting 20 does not significantly tilt, wherein the first pivot point PI and the second pivot point P2 both move downward and forward.

[0062] In the process of transforming the mechanical stretching device from the TV position shown in Fig. 6 or Fig. 9 to the lying position shown in Fig. 7 or Fig. 10, the electric drive device 4 continues to operate so that the motor slider 43 further slides along the motor rail 42 towards the motor head 41, so that the distance between the motor head 41 and the motor slider 43 is further reduced. In this process, the motor slider 43 continues to move the side plate 140 forward, i.e. in the direction of the leg stretching device 3, through the motor link 44, and the front swing lever 12 and the rear swing lever 13 swing forward to a greater extent accordingly. When the front swing lever 12 and the rear swing lever 13 swing to the maximum extent, the side plate 140 moves significantly forward relative to the central linkage 15, so that the spacing between the third pivot point P3 between the central linkage 15 and the first backrest link 21 and the second pivot point P2 between the side plate 140 and the second backrest link 22 increases, and further causes the backrest link assembly to compress while moving forward, and the backrest mounting 20 rotates sharply backward around the first pivot point PI. In this process, not only do the first pivot point PI and the second pivot point P2 both move forward, but the spacing between the first pivot point PI and the second pivot point P2 also significantly decreases compared to the sitting position and the TV position.

[0063] The back frame 52 can have various shapes as desired. In the embodiment shown in Figs. 8-9, for example, the back frame 52 includes a lower frame section 52a configured for fixed connection to the back mount 20 and an upper frame section 52b that transitions with the lower frame section 52a in a stepped section having a generally arcuately extending lower edge in side view as shown in Figs. 8-9. Correspondingly, the rear portion of the armrest frame 51 also has an arcuately extending section, thereby creating a gap between the armrest frame 51 and the upper frame section 52b. In transitioning from the sitting / TV position to the lying position, the back assembly 2 moves forward as a whole with the side plate 140, and the gap between the armrest frame 51 and the upper frame section 52b remains substantially constant during this process, thereby allowing for attachment of a so-called "T-back" on the back frame 52. This design not only improves the comfort of use for the user, but also significantly improves the aesthetic effect of the seat unit.

[0064] The foregoing description has been set forth in terms of a specific embodiment of the application. It is to be understood that persons skilled in the art can make any modifications to the specific embodiment of the application without departing from the scope of the claims of the application. Accordingly, the scope of the claims of the application is not limited only to the foregoing specific embodiment.

[0065] BIBLIOGRAPHY 1 11 base assembly 112 base longitudinal beam 113 base front cross beam 12 base rear cross beam 13 front swing lever 140 rear swing lever 141 side plate 142 first linkage 143 second linkage 15 third linkage 16 central linkage 17 seat section linkage 18 side plate linkage 19 first transmission member 2 second transmission member 20 backrest assembly 21 backrest mounting member 22 first backrest link 23 second backrest link 3 third backrest link 31 leg stretching device 32 first leg link 33 second leg link 34 third leg link 35 fourth leg link 36 first foot rest member 37 linkage lever 38 second foot rest member 381 foot rest extension assembly 382 first extension member 4 second extension member 40 electric drive device 41 motor cross beam 42 motor head 43 motor slide rail 44 motor link

Claims

1. Mechanical extension device for a movable seating unit, the mechanical extension device comprising: - a base assembly (11) fixedly supported on the ground; - a side plate (140) movably supported above the base assembly (11) for attaching a seat part of a seating unit; - a backrest assembly (2) pivotally connected to a rear part of the side plate (140) comprising a backrest mount (20) and a backrest linkage assembly; and - a central link (15) movably connected between the side plate (140) and the backrest assembly (2); wherein the backrest linkage assembly comprises a first backrest link (21) and a second backrest link (22), an upper end of the first backrest link (21) is hinged at a first pivot point (PI) to a front end of the backrest mount (20), a front end of the second backrest link (22) is hinged at a second pivot point (P2) to the side plate (140), and a middle part of the second backrest link (22) is hinged to a middle part of the first backrest link (21); - a leg extension device (3) pivotally connected to a front part of the side plate (140) comprising a plurality of links pivotally connected to each other, a first foot rest (35) for attaching a foot rest; the mechanical extension device enables the seating unit to be transformed at least between a sitting position in which the first foot rest (35) is stowed under the seat part and a lying position in which the backrest is reclined backwards and the first foot rest (35) is forwardly and extended compared to the sitting position, and wherein a distance between the first pivot point (PI) and the second pivot point (P2) is reduced in the lying position compared to the sitting position.

2. The mechanical stretching device of claim 1, wherein, The backrest linkage assembly is caused to compress and extend by a relative movement of the central link (15) and the side plate (140) to enable a rotation of the backrest mount (20) around the first pivot point (PI) backwards and forwards.

3. The mechanical stretching device of claim 2, wherein, The backrest linkage assembly further comprises a third backrest link (23), wherein a lower end of the first backrest link (21) is hinged at a third pivot point (P3) to the central link (15), an upper end of the third backrest link (23) is hinged to a rear end of the backrest mount (20), and a lower end of the third backrest link (23) is hinged to a rear end of the second backrest link (22).

4. The mechanical stretching device of claim 3, wherein, A relative movement between the side plate (140) and the central link (15) during a transformation of the seating unit from the sitting position to the lying position causes a distance between the second pivot point (P2) and the third pivot point (P4) to increase, thereby enabling a compression of the backrest linkage assembly.

5. The mechanical stretching device of claim 1, wherein, The leg stretching device (3) further comprises a second footrest (37), in the sitting position, both the first footrest (35) and the second footrest (37) are retracted under the seat part, in the lying position, the backrest is reclined, the highest point of the footstool is higher than the highest point of the backrest, wherein both the first footrest (35) and the second footrest (37) extend forward and upward, and the second footrest (37) is located in front of the first footrest (35).

6. The mechanical stretching device of claim 5, wherein, The first footrest (35) and the second footrest (37) are connected by a footrest extension assembly (38), the footrest extension assembly (38) comprises a first extension piece (381) and a second extension piece (382) hinged to each other.

7. The mechanical stretching device of claim 1, wherein, The mechanical stretching device further comprises a front swing rod (12), a rear swing rod (13), a seat part linkage (16) and a side plate linkage (17), wherein the lower ends of the front swing rod (12) and the rear swing rod (13) are respectively pivotally connected with the base assembly (11), and the upper ends of the front swing rod (12) and the rear swing rod (13) are connected with the side plate (140) through the central linkage (15), the seat part linkage (16) and the side plate linkage (17).

8. The mechanical stretching device of claim 7, wherein, The movement of the side plate (140) relative to the base assembly (11) causes the movement of the backrest assembly (2) and the leg stretching device (3) relative to the side plate (140), thereby realizing the transformation of the seat unit between the sitting position and the lying position.

9. The mechanical stretching device of claim 1, wherein, In the lying position, the highest point of the first footrest (35) is higher than the highest point of the backrest mounting (20).

10. The mechanical stretching device of claim 1, wherein, The mechanical stretching device further comprises an electric drive device (4) coupled between the base assembly (11) and the side plate (140).

11. A seat unit according to claim one, said seat unit comprising: The mechanical stretching device according to any one of claims 1 to 10 and a frame assembly connected with the mechanical stretching device, the frame assembly comprising: a seat part frame (50) fixedly attached to the side plate (140) and used to support the seat part (500) of the seat unit; an armrest frame (51) fixedly attached to both sides of the seat part frame (50); a backrest frame (52) fixedly attached to the backrest mounting (20) and used to support the backrest (520) of the seat unit.

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