Elderly chair lifting drive mechanism, seat frame and seat

Abstract

The present invention relates to a lifting drive mechanism of an elderly chair, comprising a base frame, a driving assembly and a lifting assembly; the lifting assembly comprises a lifting connection plate, a first lifting link, a second lifting link and a support seat, the support seat is fixedly connected to the base frame, one end of the first lifting link and the second lifting link are respectively rotatably connected to the support seat, and the other ends of the first lifting link and the second lifting link are respectively rotatably connected to the lifting connection plate; the driving assembly comprises a driving rod, a push rod connecting piece, and a lifting connection piece; a push rod connecting piece is provided in the middle of the driving rod, the push rod connecting piece is used to connect with the push rod of the driving source, the two ends of the driving rod are respectively connected to the lifting connection piece, and the lifting connection piece is connected to the lifting connection plate. The present application improves the connection method of the rod member driving the lifting so that the force points are concentrated at both ends, the lifting process is more stable, no shaking occurs, and materials are saved, and the weight of the entire seat frame is reduced.

Description

Technical Field

[0001] The invention relates to the field of furniture, and in particular to a lifting drive mechanism of an elderly chair, a seat frame and a seat. Background Art

[0002] With the development of science and technology and the improvement of people's living standards, people have higher and higher requirements for the versatility of seating units. The function of the elderly chair is mainly to help the elderly with inconvenient legs and feet and poor waist strength to stand up from the sofa, making it easier for the elderly to move.

[0003] In the prior art, in order to make the lifting part structure stable and increase the comfort, the elderly chair adopts the installation of the whole frame. For example, the application number 201810007860.6 discloses a mechanical device for the elderly chair, wherein the rod for driving in the prior art is specifically set as follows: the lifting square frame is connected to the chassis through the twelfth rotating shaft, the lifting frame is connected to the lifting square frame through the fourteenth rotating shaft, and the lifting connecting rod is connected to the lifting frame and the chassis through the thirteenth rotating shaft and the fifteenth rotating shaft respectively; the welding connecting piece is connected to the lifting frame through the sixteenth rotating shaft 1, and the square tube of the adjustable connecting piece is inserted into the square tube of the welding connecting piece, thereby realizing the function of adjusting the width. When the motor push rod continues to move forward, the lifting square frame and the lifting connecting rod connected to the chassis through the twelfth rotating shaft and the fifteenth rotating shaft of the lifting base move upward around the rotating shaft, so that the lifting frame connected to the lifting square frame and the lifting connecting rod through the thirteenth rotating shaft and the fourteenth rotating shaft is lifted, and the left and right sides fixed on the lifting frame and kept relatively still are lifted together, so that the mechanical extension device of the elderly chair realizes the process of switching states.

[0004] However, in the prior art, the square tube of the adjustable connector is inserted into the square tube of the welded connector in order to enable the welded connector to simultaneously realize the two functions of lifting and lowering and adjusting the state of the telescopic mechanism. However, such a setting causes the adjustable connector to be not stable enough and is prone to shaking during movement. The overall structural stability is poor, and due to structural limitations, the product manufacturing efficiency is low, the cumulative error is large, and the precision is low. However, due to the existence of the welding frame, it can only be set in this way, and its stability effect cannot be further improved.

[0005] Therefore, it is necessary to provide a lifting drive mechanism for an elderly chair that can achieve stable force during the driving process to solve the above problems. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a lifting drive mechanism, a seat frame and a seat for an elderly chair. By improving the connection method of the rods that drive the lifting, the force points are concentrated at both ends, the lifting process is more stable and not prone to shaking, and materials are saved, reducing the weight of the entire seat frame.

[0007] The technical effects of the present invention are achieved as follows:

[0008] A lifting drive mechanism for an elderly chair, comprising a base frame, a driving assembly and a lifting assembly;

[0009] The lifting assembly comprises a lifting connection plate, a first lifting link, a second lifting link and a support seat, wherein the support seat is fixedly connected to the base frame, one end of the first lifting link and the second lifting link are respectively rotatably connected to the support seat, and the other end of the first lifting link and the second lifting link are respectively rotatably connected to the lifting connection plate;

[0010] The driving assembly includes a driving rod, a push rod connecting piece, and a lifting connecting piece; a push rod connecting piece is provided in the middle of the driving rod, and the push rod connecting piece is used to connect with the push rod of the driving source, and the two ends of the driving rod are respectively connected to the lifting connecting pieces, and the lifting connecting pieces are connected to the lifting connecting plate.

[0011] Furthermore, both ends of the driving rod are provided with driving rod rivet plates, the driving rod rivet plates are riveted to the lifting connecting plates, and the telescopic driving connecting rod assembly is connected to the lifting connecting plates.

[0012] Furthermore, the other ends of the first lifting link and the second lifting link are rotatably riveted to the lifting connection plate respectively.

[0013] Furthermore, the lifting components are divided into two groups and are symmetrically arranged along the center plane of the base frame. The first lifting link is located below the second lifting link, and a first stabilizing link is provided between the two first lifting links.

[0014] Furthermore, the two support seats are arranged on the outer side of the longitudinal bottom frame of the base frame, the first lifting link is arranged on the outer side of the support seat, and the longitudinal bottom frame is used to limit the lowest descending position of the first stabilizing link.

[0015] Furthermore, a second stabilizing link is connected between the two lifting connecting plates, and the upper end of the supporting seat is used to limit the lowest descending position of the second stabilizing link.

[0016] In addition, the present application also provides a seat frame of an elderly chair, including a telescopic connecting rod assembly, a foot connecting piece, a backrest connecting piece, and the elderly chair lifting drive mechanism as described above;

[0017] The driving assembly also includes a telescopic driving link assembly, which is used to drive the telescopic link assembly to change the relative position of the foot connector and the backrest connector, and the driving assembly is used to drive the lifting and lowering of the lifting assembly; the lifting connecting plate is also connected to the driving assembly and the telescopic link assembly respectively.

[0018] Furthermore, both ends of the driving rod are also connected to the telescopic connecting rod assembly;

[0019] The lifting connection plate is an integrated plate-shaped structure, and the driving assembly and the telescopic connecting rod assembly are both riveted to the lifting connection plate.

[0020] Furthermore, both ends of the driving rod are provided with driving rod rivet plates, and the driving rod rivet plates are riveted to the lifting connecting plate and the telescopic driving connecting rod assembly at the same time.

[0021] In addition, the present application also provides a chair for the elderly, comprising a backrest support portion, a foot support portion and the seat frame of the chair for the elderly as described above, wherein the backrest support portion is connected to the backrest connector, and the foot support portion is connected to the foot connector.

[0022] As described above, the present invention has the following beneficial effects:

[0023] (1) In the present application, the two ends of the driving rod are directly connected to the lifting connecting plate for driving the entire frame to lift through the lifting connecting piece, so that the force points of the driving rod are concentrated at the two ends. Therefore, the components on both sides of the frame will not shake during the up and down driving process, and the driving rod will also remain in a taut state due to the force at both ends, and the structure is more stable and reliable;

[0024] (2) Due to the provision of a lifting connecting plate, the various components of the drive assembly can be directly riveted to it, replacing the original welding frame. The structure is lighter, and the riveting method is more precise than welding, with a smaller assembly error, which simplifies the assembly process, reduces the manufacturing cost, and improves production efficiency. In addition, all the movements of the seat frame are integrated on the lifting connecting plate used for riveting. As a separate module, the pipe fittings are also used separately, which makes it easier to match with other different bases. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0026] Figure 1 It is a structural schematic diagram of the seat frame in a sitting position according to an embodiment of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a portion of a seat frame in a sitting position according to an embodiment of the present invention;

[0028] Figure 3It is a schematic diagram of the structure of a part of the seat frame in the TV posture state according to an embodiment of the present invention;

[0029] Figure 4 It is a schematic diagram of the structure of a part of the seat frame in a lying state according to an embodiment of the present invention;

[0030] Figure 5 It is a schematic structural diagram of a portion of the seat frame in a standing position according to an embodiment of the present invention;

[0031] Figure 6 It is a schematic diagram of the structure of the lifting assembly in a sitting position according to an embodiment of the present invention;

[0032] Figure 7 It is a schematic diagram of the structure of the lifting assembly in the embodiment of the present invention when it is in a standing position;

[0033] Figure 8 It is a front view of the lifting connecting plate in the embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] like Figure 1-8 As shown, in this embodiment, a lifting drive mechanism for an elderly chair is provided, which is a part of a seat frame. It can be used for a seat unit, specifically for an elderly chair seat. In this embodiment, the elderly chair is a chair with a variable posture that can realize the lifting and tilting of the seat part, so as to assist users with inconvenient legs or feet or weak bodies to stand up.

[0037] Specifically, the driving mechanism includes a base frame 1, a driving assembly 3 and a lifting assembly 2;

[0038] The lifting assembly 2 includes a lifting connection plate 21, a first lifting link 22, a second lifting link 23 and a support seat 25, the support seat 25 is fixedly connected to the base frame 1, one end of the first lifting link 22 and the second lifting link 23 are respectively rotatably connected to the support seat 25, and the other ends of the first lifting link 22 and the second lifting link 23 are respectively rotatably connected to the lifting connection plate 21;

[0039] The driving assembly 3 includes a driving rod 31, a push rod connector 32, and a lifting connector 33; a push rod connector 32 is provided in the middle of the driving rod, and the push rod connector 32 is used to connect with the driving source push rod, and the two ends of the driving rod 31 are respectively connected to the lifting connector 33, and the lifting connector 33 is connected to the lifting connector plate 21. In the present application, the two ends of the driving rod 31 are directly connected to the lifting connector plate 21 for driving the entire frame to rise and fall through the lifting connector 33, so that the force points of the driving rod 31 are concentrated at the two ends, so that the components on both sides of the frame will not shake during the up and down driving process, and the driving rod 31 will also remain in a taut state due to the force at both ends, and the structure is more stable and reliable.

[0040] The driving source that drives the driving assembly to move is specifically the driving motor 7 , the push rod connector 32 is rotationally connected to one end of the motor push rod 71 of the driving motor 7 , and the housing 72 of the driving motor 7 is rotationally connected to the base frame 1 .

[0041] The third position and the fourth position corresponding to the extension degree of the motor push rod 71 correspond to two postures of the seat, namely, a sitting posture and a standing posture.

[0042] When the motor push rod 71 is further pushed forward from the third position to the fourth position, the seat will switch from the sitting position to the standing position. At this time, the specific process is that the motor push rod 71 drives the driving rod 31 to move forward and upward through the push rod connecting piece 32, and the driving rod 31 drives the upper end of the lifting connecting plate 21 to move through the lifting connecting piece 33. The lifting connecting plate 21 is rotatably connected with the first lifting link 22 and the second lifting link 23 at the same time, and the first lifting link 22, the second lifting link 23 and the support seat 25 fixed on the base frame 1 are rotatably connected, so that the lifting connecting plate 21 rises with a predetermined arc, and drives the telescopic link assembly 4 connected to the lifting connecting plate 21 to rise together, and the telescopic link assembly 4 is in a forward tilting state, and the motor push rod 71 reaches the fourth position, thereby forming a final standing position, so that people with weaker physical strength, such as the elderly, can stand up more effortlessly.

[0043] Preferably, both ends of the driving rod 31 are provided with driving rod rivet plates 311 , the driving rod rivet plates 311 are riveted to the lifting connection plates 33 , and the telescopic driving connecting rod assembly 34 is connected to the lifting connection plates 33 .

[0044] The other ends of the first lifting link 22 and the second lifting link 23 are respectively rotatably riveted to the lifting connection plate 21. Due to the provision of the lifting connection plate, the components of the driving assembly can be directly riveted to it, replacing the original welding frame, the structure is lighter, and the riveting method is more accurate than welding, and the assembly error is small.

[0045] Specifically, in this embodiment, the seat frame is a bilaterally symmetrical structure, the lifting assembly 2 and the telescopic link assembly 4 are both two groups and are symmetrically arranged along the center plane of the base frame 1, the first lifting link 22 is located below the second lifting link, and a first stabilizing link 24 is provided between the two first lifting links 22. The transmission methods on both sides are the same, and stable driving without error can be achieved. Specifically, in order to achieve the stability of the transmission mechanism on both sides, two support seats 25 are provided on the outer side of the longitudinal bottom frame 11 of the base frame 1, the first lifting link 22 is provided on the outer side of the support seat 25, and the longitudinal bottom frame 11 is used to limit the lowest descending position of the first stabilizing link 24.

[0046] When the seat switches from a standing position to a sitting position, during the descent of the first lifting link 22, the first stabilizing link 24 stops descending after hitting the longitudinal bottom frame 11. Therefore, the first stabilizing link 24 not only increases the stability of the first lifting link 22, so that the two first lifting links 22 will not shake relative to each other during movement, and have higher strength, but also plays a limiting and supporting role at the same time, limiting the lowest position of its descent, so that during the process of switching the seat's posture, the structure below can provide stable support.

[0047] Embodiment 2:

[0048] In the present embodiment, a seat frame of an elderly chair is provided, which includes the elderly chair lifting drive mechanism as mentioned in the embodiment 1, and further includes a telescopic link assembly 4, a foot connector 5, and a backrest connector 6. In the present embodiment, the seat frame can change into four postures, corresponding to the sitting posture, TV posture, lying posture and standing posture of the seat, wherein the sitting posture is the state of daily use of the seat, with the legs retracted and the backrest close to vertical, which is suitable for the user to sit down and rest daily, the TV posture is the state of the seat legs extended, and accordingly, the inclination angle of the backrest remains unchanged or slightly tilted backward, which is suitable for the user to relax when watching TV, and the lying posture is the state in which the legs of the seat are further raised, the backrest is further tilted backward and then descended, which is suitable for the user to lie flat and rest.

[0049] in, Figure 1 is a schematic diagram of the structure of the seat frame in a sitting position according to an embodiment of the present invention, Figure 3 It is a schematic diagram of the structure of a part of the seat frame in the TV posture state according to an embodiment of the present invention; Figure 4 It is a schematic diagram of the structure of a part of the seat frame in a lying state according to an embodiment of the present invention; Figure 5 It is a schematic structural diagram of a portion of the seat frame in a standing position according to an embodiment of the present invention;

[0050] Specifically, the telescopic link assembly 4 includes a foot link assembly 41, a back link assembly 42 and an intermediate link assembly 43. One end of a first intermediate link 431 of the intermediate link assembly 43 is rotatably connected to the backrest connector 6, and the other end is rotatably connected to the foot link assembly 41.

[0051] The back connecting rod assembly 42 includes a first backrest connecting rod 421, one end of which is rotatably connected to the backrest connecting member 6, and the other end of which is rotatably connected to the lifting connecting plate 21.

[0052] The foot link assembly 41 includes a first foot link 411, a second foot link 412, a third foot link 413 and a fourth foot link 414. One end of the first foot link 411 and the second foot link 412 are both rotatably connected to the foot connector 5, the other end of the first foot link 411 is rotatably connected to one end of the third foot link 413, and the other end of the third foot link 413 is connected to the first intermediate link 431; the other end of the second foot link 412 is rotatably connected to one end of the fourth foot link 414, the other end of the fourth foot link 414 is rotatably connected to one end of the second intermediate link 432 of the intermediate link assembly 43, and the other end of the second intermediate link 432 is rotatably connected to the lifting connection plate 21;

[0053] The telescopic drive link assembly 34 includes a telescopic drive link 341 and a telescopic drive connecting piece 342, wherein the lifting connecting piece 33 is rotatably connected to one end of the telescopic drive link 341, and the other end of the telescopic drive link 341 is rotatably connected to the telescopic drive connecting piece 342. At the same time, the telescopic drive connecting piece 342 is fixedly connected to the first intermediate link 431, which is riveted in this embodiment.

[0054] The push rod connector 32 is rotatably connected to one end of the motor push rod 71 of the drive motor 7, and the housing 72 of the drive motor 7 is rotatably connected to the base frame 1. The rotatable connection of the above-mentioned components can be riveted rotation, or can be achieved by a pin shaft, a step bolt, etc.

[0055] The motor push rod 71 can be divided into a first position, a second position, a third position and a fourth position according to its extension degree, which respectively correspond to the four postures of the seat, namely, lying posture, TV posture, sitting posture and standing posture.

[0056] When the motor push rod 71 is in the third position, that is, the sofa is in a sitting position, the foot link assembly 41 is in a retracted state. At this time, the motor push rod 71 is driven to retract, and the drive rod 31 is driven to move toward the motor housing through the push rod connector 32. The drive rod 31 drives the telescopic drive link 341 by driving the lifting connection piece 33 to rotate, thereby further driving the telescopic drive connection piece 342 to drive the first intermediate link 431 to move toward the backrest connector. The foot link assembly 41 is thus changed from a retracted state to an extended state, and finally the motor push rod 71 moves to the second position, so that it is adjusted to the TV position.

[0057] When the motor push rod 71 is in the second position, the motor push rod 71 is further retracted, and the foot connecting rod assembly 41 is further lifted. The backrest connecting member 6 is tilted backward under the drive of the first intermediate connecting rod 431. When the motor push rod 71 finally moves from the second position to the first position, the foot connecting member 5 is higher than the backrest connecting member 6 to form a lying position.

[0058] The process of switching the sofa from a lying position to a TV position and from a TV position to a sitting position is to move the motor push rod 71 from the first position to the second position and from the second position to the third position. The specific transmission relationship is opposite to the aforementioned stretching and opening process and will not be repeated here.

[0059] Embodiment 3:

[0060] In the present embodiment, a chair is provided, including a backrest support portion, a foot support portion and a seat frame, the seat frame including a base frame 1, a lifting assembly 2, a drive assembly 3 and a telescopic connecting rod assembly 4; the backrest support portion is fixedly connected to the backrest connector 6 to achieve posture change, and the foot support portion is connected to the foot connector 5 to achieve posture change. Specifically, the chair in the present embodiment can achieve a chair with a changeable posture by lifting and tilting the seat forward, which is convenient for users with mobility impairments or weak bodies to help them stand up.

[0061] Specifically, the driving mechanism includes a base frame 1, a driving assembly 3 and a lifting assembly 2;

[0062] The lifting assembly 2 includes a lifting connection plate 21, a first lifting link 22, a second lifting link 23 and a support seat 25, the support seat 25 is fixedly connected to the base frame 1, one end of the first lifting link 22 and the second lifting link 23 are respectively rotatably connected to the support seat 25, and the other ends of the first lifting link 22 and the second lifting link 23 are respectively rotatably connected to the lifting connection plate 21;

[0063] The driving assembly 3 includes a driving rod 31, a push rod connector 32, and a lifting connector 33; a push rod connector 32 is provided in the middle of the driving rod, and the push rod connector 32 is used to connect with the driving source push rod, and the two ends of the driving rod 31 are respectively connected to the lifting connector 33, and the lifting connector 33 is connected to the lifting connector plate 21. In the present application, the two ends of the driving rod 31 are directly connected to the lifting connector plate 21 for driving the entire frame to rise and fall through the lifting connector 33, so that the force points of the driving rod 31 are concentrated at the two ends, so that the components on both sides of the frame will not shake during the up and down driving process, and the driving rod 31 will also remain in a taut state due to the force at both ends, and the structure is more stable and reliable.

[0064] As described above, the present invention has the following beneficial effects:

[0065] (1) In the present application, the two ends of the driving rod are directly connected to the lifting connecting plate for driving the entire frame to lift through the lifting connecting piece, so that the force points of the driving rod are concentrated at the two ends. Therefore, the components on both sides of the frame will not shake during the up and down driving process, and the driving rod will also remain in a taut state due to the force at both ends, and the structure is more stable and reliable;

[0066] (2) Due to the provision of a lifting connecting plate, the various components of the drive assembly can be directly riveted to it, replacing the original welding frame. The structure is lighter, and the riveting method is more precise than welding, with a smaller assembly error. The assembly process is simplified, the production cost is reduced, and the production efficiency is improved. In addition, all the movements of the seat frame are integrated on the lifting connecting plate used for riveting. As a separate module, the pipe fittings are also used separately, which makes it easier to match with other different bases.

[0067] In this document, the directional words such as front, back, top, and bottom are defined by the positions of the components in the drawings and the positions of the components relative to each other, and are only for the sake of clarity and convenience in expressing the technical solution. It should be understood that the use of the directional words should not limit the scope of protection claimed in this application.

[0068] In the absence of conflict, the above embodiments and features in the embodiments can be combined with each other.

[0069] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A lifting drive mechanism for an elderly chair, characterized in that: It comprises a base frame (1), a driving assembly (3) and a lifting assembly (2); The lifting assembly (2) comprises a lifting connection plate (21), a first lifting link (22), a second lifting link (23) and a support seat (25), wherein the support seat (25) is fixedly connected to the base frame (1), one end of the first lifting link (22) and the second lifting link (23) are respectively rotatably connected to the support seat (25), and the other end of the first lifting link (22) and the second lifting link (23) are respectively rotatably connected to the lifting connection plate (21); The driving assembly (3) comprises a driving rod (31), a push rod connecting piece (32), a lifting connecting piece (33) and a telescopic driving connecting rod assembly (34); a push rod connecting piece (32) is provided in the middle of the driving rod, the push rod connecting piece (32) is used to be connected to a push rod of a driving source, and both ends of the driving rod (31) are respectively connected to the lifting connecting pieces (33), and the lifting connecting piece (33) is connected to the lifting connecting plate (21); Both ends of the driving rod (31) are provided with driving rod riveting plates (311), the driving rod riveting plates (311) are riveted to the lifting connecting plates (33), and the telescopic driving connecting rod assembly (34) is connected to the lifting connecting plates (33); The lifting components (2) are divided into two groups and are symmetrically arranged along the center plane of the base frame (1); the first lifting link (22) is located below the second lifting link; a first stabilizing link (24) is arranged between the two first lifting links (22); the two support seats (25) are arranged on the outer side surface of the longitudinal bottom frame (11) of the base frame (1); the first lifting link (22) is arranged on the outer side surface of the support seat (25); and the longitudinal bottom frame (11) is used to limit the lowest descending position of the first stabilizing link (24).

2. The lifting drive mechanism of the elderly chair according to claim 1, characterized in that: The other ends of the first lifting link (22) and the second lifting link (23) are rotatably riveted to the lifting connection plate (21) respectively.

3. The lifting and driving mechanism of the elderly chair according to claim 2, characterized in that: A second stabilizing link (35) is connected between the two lifting connection plates (21), and the upper end of the support seat (25) is used to limit the lowest descending position of the second stabilizing link (35).

4. A seat frame for an elderly chair, characterized in that: It comprises a telescopic connecting rod assembly (4), a foot connecting piece (5), a backrest connecting piece (6) and a lifting drive mechanism for an elderly chair as claimed in any one of claims 1 to 3; The driving assembly (3) is used to drive the telescopic connecting rod assembly (4) to change the relative position of the foot connecting member (5) and the backrest connecting member (6), and the driving assembly (3) is used to drive the lifting and lowering of the lifting assembly (2); the lifting connecting plate (21) is also connected to the driving assembly (3) and the telescopic connecting rod assembly (4), respectively.

5. The seat frame of an elderly chair according to claim 4, characterized in that: Both ends of the driving rod (31) are also connected to the telescopic connecting rod assembly (4); The lifting connection plate (21) is an integrated plate-shaped structure, and the driving assembly (3) and the telescopic connecting rod assembly (4) are both riveted to the lifting connection plate (21).

6. The seat frame of an elderly chair according to claim 5, characterized in that: Both ends of the driving rod (31) are provided with driving rod riveting plates (311), and the driving rod riveting plates (311) are simultaneously riveted to the lifting connecting plate (33) and the telescopic driving connecting rod assembly (34).

7. An elderly chair, characterized in that: It comprises a backrest support part, a foot support part and a seat frame of an elderly chair as described in claims 4 to 6, wherein the backrest support part is connected to the backrest connecting piece (6), and the foot support part is connected to the foot connecting piece (5).

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