Backrest mechanism and seat iron stand

Abstract

The utility model relates to the technical field of seats, in particular to a backrest mechanism and a seat iron stand, the backrest mechanism comprises a four-connecting-rod group and a driving piece, the four-connecting-rod group comprises a first connecting rod, a second connecting rod, a third connecting rod and a fourth connecting rod which are hinged in sequence and form a ring, and the driving piece is arranged on a suspension mechanism and connected with the four-connecting-rod group. The seat frame support can move relative to the hanging mechanism in the preset direction so that the driving piece can drive the four-connecting-rod set to change the shape. The angle and the position of the backrest can be adjusted by setting the moving distance of the hinge point of the third connecting rod and the fourth connecting rod, and the backrest and the seat frame are connected through the four-connecting-rod group, so that the problem that the backrest is too close to the wall, and movement interference occurs between the backrest and the wall can be solved; and therefore, smooth switching of various modes of the seat iron stand cannot be realized.

Description

[0001] This application is a divisional application of the following application: the application date is May 31, 2023, the application number is 202321353450.X, and the patent name is backrest mechanism and seat iron frame. Technical Field

[0002] The utility model relates to the technical field of seats, in particular to a backrest mechanism and a seat iron frame. Background Art

[0003] With the development of society, people's pursuit of quality of life is constantly improving. When choosing furniture, consumers are no longer limited to a single function, but more hope to maximize the utilization rate of furniture, which is the modern thinking. For example, for chairs or sofas, consumers are more pursuing comfort, such as the ability to provide multiple usage modes such as reading and lying flat. With the continuous deepening of research and development, some functional sofas have also appeared on the market, but these sofas still have shortcomings in terms of multi-mode use.

[0004] For example, when the sofa is placed against a wall, when switching between different modes, if the distance between the backrest and the wall is too close, there will be movement interference between the sofa backrest and the wall, and smooth switching of the sofa mode cannot be achieved. Utility Model Content

[0005] The utility model aims to provide a backrest mechanism and a seat iron frame to solve the problem in the related art that if the distance between the backrest and the wall is too close, there will be movement interference between the sofa backrest and the wall, and thus the sofa cannot be smoothly switched between different modes.

[0006] On the one hand, the utility model provides a backrest mechanism for a seat iron frame, wherein the seat iron frame comprises a suspension mechanism and a seat frame bracket hinged thereto, and the backrest mechanism comprises:

[0007] A four-bar linkage and a driving member, wherein the four-bar linkage comprises a first link, a second link, a third link and a fourth link which are hinged in sequence and arranged in a ring shape, the driving member is arranged on the suspension mechanism and connected to the four-bar linkage, and the seat frame bracket can move relative to the suspension mechanism in a preset direction so that the driving member can drive the four-bar linkage to change its shape.

[0008] As a preferred technical solution of the backrest mechanism, the first connecting rod is fixedly connected to the seat frame bracket, and the driving member drives the second connecting rod to rotate around a hinge point between the second connecting rod and the first connecting rod.

[0009] As an optimal technical solution for the backrest mechanism, the second connecting rod is hinged to one end of the first connecting rod and one end of the third connecting rod respectively; the fourth connecting rod is located on one side of the second connecting rod and is hinged to one end of the first connecting rod away from the second connecting rod and one end of the third connecting rod away from the second connecting rod respectively.

[0010] As a preferred technical solution for the backrest mechanism, the driving member is a driving rod, one end of the driving rod is hinged to the suspension mechanism, one end of the second connecting rod is hinged to the third connecting rod, the other end is hinged to the other end of the driving rod, and the middle part of the second connecting rod is hinged to the first connecting rod.

[0011] As a preferred technical solution of the backrest mechanism, the third connecting rod is provided with a first limiting protrusion, the first limiting protrusion is located between the second connecting rod and the fourth connecting rod, the first connecting rod is provided with a second limiting protrusion, and the second limiting protrusion is located on a side of the fourth connecting rod away from the second connecting rod;

[0012] Either the first limiting protrusion or the second limiting protrusion abuts against the fourth connecting rod.

[0013] On the other hand, the utility model further provides a chair iron frame, comprising the backrest mechanism described in any one of the above schemes, and the chair iron frame also includes:

[0014] Suspension mechanism;

[0015] A seat frame bracket is hinged to the suspension mechanism;

[0016] The seat frame bracket can move relative to the suspension mechanism along the preset direction, so that the driving member can drive the four-bar linkage to change its shape.

[0017] As an optimal technical solution for the seat iron frame, it also includes a footrest retractable mechanism, which is fixed to the seat frame bracket and includes an extension rod group, a main footrest and an auxiliary footrest assembly. The extension rod group drives the main footrest and the auxiliary footrest assembly to extend or retract relative to the seat frame bracket.

[0018] As a preferred technical solution for the seat iron frame, the stretching rod group includes a first stretching rod, a second stretching rod, a third stretching rod and a fourth stretching rod, the first stretching rod is hinged to the second stretching rod, the third stretching rod is hinged to the fourth stretching rod, the middle part of the first stretching rod is cross-hinged to the middle part of the fourth stretching rod, the first stretching rod and the third stretching rod are respectively hinged to the seat frame bracket, and the second stretching rod and the fourth stretching rod are respectively hinged to the main footrest.

[0019] As an optimal technical solution for the iron frame of the seat, the auxiliary footrest assembly includes an auxiliary footrest and a secondary connecting rod, the two ends of the secondary connecting rod are respectively hinged to the auxiliary footrest and the main footrest, the middle part of the second extension rod is hinged to the main footrest; one end of the second extension rod away from the first extension rod is hinged to the auxiliary footrest.

[0020] As a preferred technical solution of the seat iron frame, the suspension mechanism includes a first rod, a second rod and a third rod, and the first rod, the second rod, the third rod and the seat frame bracket are hinged end to end in sequence and surrounded to form a first annular four-bar structure;

[0021] The suspension mechanism further includes a fourth rod, a fifth rod, a sixth rod and a seventh rod, the middle portion of the fourth rod is hinged to one end of the fifth rod, the other end of the fifth rod is hinged to one end of the sixth rod, the other end of the sixth rod is hinged to the middle portion of the seventh rod, one end of the seventh rod is hinged to one end of the fourth rod, and the fourth rod, the fifth rod, the sixth rod and the seventh rod are arranged to form a second annular four-bar structure;

[0022] The suspension mechanism also includes a first connecting rod and a second connecting rod, the first connecting rod includes a first connecting support rod and a second connecting support rod, one end of the first connecting support rod is hinged to the other end of the fourth rod, the other end of the first connecting support rod is hinged to the middle of the second rod, one end of the second connecting support rod is hinged to the middle of the fourth rod, the hinged end of the second rod and the first rod is hinged to the other end of the second connecting support rod, one end of the second connecting rod is hinged to the middle of the sixth rod, and the other end of the second connecting rod is hinged to the second rod.

[0023] As an optimal technical solution for the iron frame of the seat, it also includes a connecting rod, one end of which is hinged to the third extending rod, and the other end of the connecting rod is hinged to the third rod, the distance between the hinge point between the connecting rod and the third extending rod and the hinge point between the third extending rod and the seat frame bracket is 22mm-26mm, and the distance between the two hinge points at both ends of the third extending rod is 18cm-22cm.

[0024] The beneficial effects of the utility model are:

[0025] The utility model provides a backrest mechanism and a seat iron frame, the backrest mechanism includes a four-link group and a driving member, the four-link group includes a first link, a second link, a third link and a fourth link that are hinged in sequence and arranged in a ring, the driving member is arranged on the suspension mechanism and connected to the four-link group, the seat frame bracket can move relative to the suspension mechanism along a preset direction, so that the driving member can drive the four-link group to change shape. When the seat iron frame equipped with the backrest mechanism is adjusted to the seat mode, the seat frame bracket is driven to move relative to the suspension mechanism along a preset direction, and the driving member can drive the four-link group to change shape, and the angle and relative position of the backrest and the ground can be changed, so that the shape of the seat iron frame can be switched. Specifically, during the process of changing the shape of the four-link group, the distance of the hinge point movement of the third link and the fourth link determines the change of the angle and position of the backrest relative to the ground. Since the backrest and the seat frame are connected by the four-link group, the problem that the distance between the backrest and the wall is too close, the backrest and the wall will have motion interference, and the various modes of the seat iron frame cannot be smoothly switched can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structure diagram of the sitting posture mode of the chair iron frame in the first embodiment of the utility model is shown in FIG. Figure 1 ;

[0027] Figure 2 The structure diagram of the sitting posture mode of the chair iron frame in the first embodiment of the utility model is shown in FIG. Figure 2 ;

[0028] Figure 3 The structure of the TV mode of the seat iron frame in the first embodiment of the utility model is shown in FIG. Figure 1 ;

[0029] Figure 4 The structure of the TV mode of the seat iron frame in the first embodiment of the utility model is shown in FIG. Figure 2 ;

[0030] Figure 5 The structure of the lying position mode of the seat iron frame in the first embodiment of the utility model is shown in FIG. Figure 1 ;

[0031] Figure 6 The structure of the lying position mode of the seat iron frame in the first embodiment of the utility model is shown in FIG. Figure 2 ;

[0032] Figure 7 It is a structural schematic diagram of the sitting posture mode of the chair iron frame in the second embodiment of the present utility model.

[0033] In the figure:

[0034] 1. Suspension mechanism; 11. First rod; 12. Second rod; 13. Third rod; 14. Fourth rod; 15. Fifth rod; 16. Sixth rod; 17. Seventh rod; 18. First connecting rod; 19. Second connecting rod;

[0035] 2. Seat frame bracket;

[0036] 3. Backrest mechanism; 31. Four-link group; 311. First link; 3111. Second limit protrusion; 312. Second link; 313. Third link; 3131. First limit protrusion; 314. Fourth link; 32. Driving member;

[0037] 4. Foot pedal retractable mechanism; 41. Extension rod group; 411. First extension rod; 412. Second extension rod; 413. Third extension rod; 414. Fourth extension rod; 42. Main foot pedal; 43. Second foot pedal assembly; 431. Second foot pedal; 432. Second connecting rod;

[0038] 5. Connecting rod. DETAILED DESCRIPTION

[0039] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0040] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are orientations or positional relationships based on the drawings, and are 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 therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0043] Embodiment 1

[0044] like Figure 1 to Figure 6As shown, the present embodiment provides a chair iron frame, which includes a suspension mechanism 1, a seat frame bracket 2 and a backrest mechanism 3, wherein the seat frame bracket 2 is hinged to the suspension mechanism 1; the backrest mechanism 3 includes a four-link group 31 and a driving member 32, the four-link group 31 includes a first link 311, a second link 312, a third link 313 and a fourth link 314 which are hinged in sequence and arranged in a ring, the first link 311 is fixedly connected to the seat frame bracket 2, wherein the first link 311 and the seat frame bracket 2 can be fixedly connected by multiple screws or rivets, or can be made in one piece, the driving member 32 is arranged on the suspension mechanism 1, and is connected to the second link 312, the seat frame bracket 2 can move relative to the suspension mechanism 1 along a preset direction, so that the driving member 32 can drive the second link 312 to rotate around the hinge point between the second link 312 and the first link 311. The seat mode of the chair iron frame includes a sitting mode, a TV mode and a lying mode. When adjusting from the sitting mode to the TV mode, the angle relationship between the connecting rods of the backrest mechanism 3 is almost unchanged during the process of driving the seat frame bracket 2 to move relative to the suspension mechanism 1 in the preset direction. The backrest mechanism 3 moves forward slightly with the seat frame bracket 2, resulting in a gap between the backrest set on the backrest mechanism 3 and the wall. When adjusting from the TV mode to the lying mode, the seat frame bracket 2 continues to move forward and slightly lifts upward, and the driving member 32 can drive the second connecting rod 312 to swing around the hinge point, thereby changing the shape of the four-link group 31 surrounded by the first connecting rod 311, the second connecting rod 312, the third connecting rod 313 and the fourth connecting rod 314. In this process, the angle and relative position between the third connecting rod 313 and the ground are constantly changing, and the distance between the vertex of the third connecting rod 313 and the wall is reduced, resulting in the distance between the backrest set on the backrest mechanism 3 and the wall being infinitely close to 0. Since the third connecting rod 313 is connected to the backrest, the process can change the angle between the backrest and the ground, and then switch the shape of the seat iron frame. Since the backrest and the seat frame are connected by the four-link group 31, the problem that the distance between the backrest and the wall is too close, there will be movement interference between the backrest and the wall, and the problem that the various modes of the seat iron frame cannot be smoothly switched can be solved.

[0045] Specifically, the seat frame bracket 2 is used to install the seat frame. The seat iron frame can be applied to sofas, wheelchairs, car seats, etc.

[0046] Optionally, the second connecting rod 312 is hinged to one end of the first connecting rod 311 and one end of the third connecting rod 313 respectively; the fourth connecting rod 314 is located on one side of the second connecting rod 312 and is hinged to one end of the first connecting rod 311 away from the second connecting rod 312 and one end of the third connecting rod 313 away from the second connecting rod 312 respectively. The driving member 32 includes a driving rod, one end of which is hinged to the suspension mechanism 1, one end of the second connecting rod 312 is hinged to the third connecting rod 313, and the other end is hinged to the other end of the driving rod, and the middle part of the second connecting rod 312 is hinged to the first connecting rod 311. In this embodiment, the driving rod drives the other end of the second connecting rod 312 to move, thereby causing the second connecting rod 312 to rotate around the first connecting rod, thereby changing the angle and relative position between the third connecting rod 313 and the ground.

[0047] Specifically, the second connecting rod 312 is arranged to be circularly bent at the intersection point with the first connecting rod 311, and the bending angle is an obtuse angle.

[0048] Optionally, the suspension mechanism 1 includes a first rod 11, a second rod 12, and a third rod 13, and the first rod 11, the second rod 12, the third rod 13 and the seat frame bracket 2 are hinged end to end in sequence and are arranged to form a first annular four-bar structure. In this embodiment, the first rod 11, the second rod 12, the third rod 13 and the seat frame bracket 2 are arranged to form an annular four-bar structure, so that the seat frame bracket 2 can move relative to the second rod 12 along a preset direction.

[0049] Optionally, the suspension mechanism 1 further includes a fourth rod 14, a fifth rod 15, a sixth rod 16 and a seventh rod 17, the middle portion of the fourth rod 14 is hinged to one end of the fifth rod 15, the other end of the fifth rod 15 is hinged to one end of the sixth rod 16, the other end of the sixth rod 16 is hinged to the middle portion of the seventh rod 17, one end of the seventh rod 17 is hinged to one end of the fourth rod 14, and the fourth rod 14, the fifth rod 15, the sixth rod 16 and the seventh rod 17 are arranged to form a second annular four-bar structure; the suspension mechanism 1 further includes a first connecting rod 18 and a second connecting rod 19 The first connecting rod 18 includes a first connecting rod 181 and a second connecting rod 182, one end of the first connecting rod 181 is hinged to the other end of the fourth rod 14, the other end of the first connecting rod 181 is hinged to the middle of the second rod 12, one end of the second connecting rod 182 is hinged to the middle of the fourth rod 14, the hinged end of the second rod 12 and the first rod 11 is hinged to the other end of the second connecting rod 182, one end of the second connecting rod 19 is hinged to the middle of the sixth rod 16, and the other end of the second connecting rod 19 is hinged to the second rod 12. In this embodiment, the second annular four-bar structure composed of the fourth rod 14, the fifth rod 15, the sixth rod 16 and the seventh rod 17 is hinged to the four-bar group 31, and specifically, the driving rod is hinged to the other end of the seventh rod 17.

[0050] Optionally, the seat iron frame further includes a pedal telescopic mechanism 4, which includes an extension rod group 41, a main pedal 42 and an auxiliary pedal assembly 43, and the extension rod group 41 drives the main pedal 42 and the auxiliary pedal assembly 43 to extend or retract relative to the seat frame bracket 2. In this embodiment, when the main pedal 42 and the auxiliary pedal assembly 43 are in the extended position, the person sitting on the seat can put his feet on the main pedal 42 and the auxiliary pedal assembly 43, thereby improving the comfort of the person sitting on the seat.

[0051] Specifically, the stretching rod group 41 includes a first stretching rod 411, a second stretching rod 412, a third stretching rod 413 and a fourth stretching rod 414. The first stretching rod 411 is hinged to the second stretching rod 412, the third stretching rod 413 is hinged to the fourth stretching rod 414, the middle part of the first stretching rod 411 is hinged to the middle part of the fourth stretching rod 414, the first stretching rod 411 and the third stretching rod 413 are respectively hinged to the seat frame bracket 2, and the second stretching rod 412 and the fourth stretching rod 414 are respectively hinged to the main footrest 42. In this embodiment, by rotating the first stretching rod 411 relative to the seat frame bracket 2, the stretching rod group 41 can drive the main footrest 42 and the auxiliary footrest assembly 43 to extend or retract relative to the seat frame bracket 2.

[0052] Optionally, the auxiliary footrest assembly 43 includes an auxiliary footrest 431 and an auxiliary connecting rod 432, the two ends of the auxiliary connecting rod 432 are respectively hinged to the auxiliary footrest 431 and the main footrest 42, the middle part of the second extension rod 412 is hinged to the main footrest 42; one end of the second extension rod 412 away from the first extension rod 411 is hinged to the auxiliary footrest 431. In this embodiment, when the main footrest 42 is switched to the extended state, the second extension rod 412 drives the auxiliary footrest 431 to move, thereby making the auxiliary footrest 431 and the main footrest 42 both in the extended state.

[0053] Optionally, the seat iron frame further includes a driver, the driver is fixedly connected to the seventh rod 17, and the telescopic end of the driver is hinged to the first extension rod 411, and the telescopic end of the driver is telescopic along a preset direction. In this embodiment, the telescopic end of the driver is hinged to the first extension rod 411, and in the process of driving the first extension rod 411 to rotate around the seat frame bracket 2, the seat frame bracket 2 is also driven to move along the preset direction.

[0054] Optionally, two suspension mechanisms 1, backrest mechanisms 3 and footrest telescopic mechanisms 4 are provided, the two suspension mechanisms 1 are spaced and symmetrically arranged along a direction perpendicular to the preset direction, the two backrest mechanisms 3 are spaced and symmetrically arranged along a direction perpendicular to the preset direction, the two footrest telescopic mechanisms 4 are spaced and symmetrically arranged along a direction perpendicular to the preset direction, the seat frame bracket 2 is provided between the two suspension mechanisms 1, and the two sides of the seat frame bracket 2 are respectively hinged to the first rod 11 and the third rod 13 of the two suspension mechanisms 1. The backrest is provided between the two backrest mechanisms 3, and the two sides of the backrest are respectively fixed to the two third connecting rods 313.

[0055] Optionally, the seat iron frame further includes a linkage rod 5, one end of which is hinged to the third extension rod 413, and the other end of which is hinged to the third rod 13, and the distance between the hinge point between the linkage rod 5 and the third extension rod 413 and the hinge point between the third extension rod 413 and the seat frame bracket 2 is 22mm-26mm, and the distance between the two hinge points at both ends of the third extension rod 413 is 18cm-22cm. In this embodiment, the movement of the first annular four-bar structure drives the movement of the linkage rod 5, and the movement of the linkage rod 5 causes the third extension rod 413 to rotate relative to the seat frame bracket 5, thereby switching the foot pedal telescopic mechanism 4 between the extended or retracted position. Specifically, the distance between the hinge point between the linkage rod 5 and the third extension rod 413 and the hinge point between the third extension rod 413 and the seat frame bracket 2 is 22mm-26mm, and the distance between the two hinge points at both ends of the third extension rod 413 is 18cm-22cm. This setting determines the minimum ground clearance of the seat iron frame.

[0056] Optionally, the third connecting rod 313 is provided with a first limiting protrusion 3131, the first limiting protrusion 3131 is located between the second connecting rod 312 and the fourth connecting rod 314, the first connecting rod 311 is provided with a second limiting protrusion 3111, the second limiting protrusion 3111 is located on the side of the fourth connecting rod 314 away from the second connecting rod 312; the first limiting protrusion 3131 and the second limiting protrusion 3111 are selectively abutted with the fourth connecting rod 314. In this embodiment, when the sitting iron frame is in the sitting mode or the TV mode, the second limiting protrusion 3111 abuts with the fourth connecting rod 314, thereby ensuring the stability of the backrest mechanism. When the sitting iron frame is in the lying mode, the first limiting protrusion 3131 abuts with the fourth connecting rod 314, thereby ensuring the stability of the backrest mechanism.

[0057] The chair iron frame includes three modes, namely sitting mode, TV mode and lying mode. In the sitting mode, the footrest retractable mechanism 4 is in a retracted state, and the angle between the backrest mechanism 3 and the seat frame bracket 2 is between 90° and 135°; when the chair iron frame switches from the sitting mode to the TV mode, the driver drives the first extension rod 411 to rotate around the seat frame bracket 2. At this time, the auxiliary footrest 431 and the main footrest 42 are both in an extended state; when the chair iron frame switches from the TV mode to the lying mode, the driver continues to drive the first extension rod 411. At this time, the first extension rod 411 no longer swings relative to the seat frame bracket 2, but drives the seat frame bracket 2 to move relative to the suspension mechanism 1 along a preset direction. At this time, the angle between the backrest mechanism 3 and the seat frame bracket 2 changes accordingly, thereby switching the chair iron frame to the lying mode.

[0058] Embodiment 2

[0059] like Figure 7As shown, this embodiment is basically the same as the first embodiment, and the only difference is that the second connecting rod 312 is bent twice, and this setting is determined according to the force condition of the second connecting rod 312 when the driving rod drives the second connecting rod 312.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A backrest mechanism for a seat iron frame, the seat iron frame comprising a suspension mechanism (1) and a seat frame bracket (2) hinged thereto, characterized in that: include: A four-bar linkage (31) and a driving member (32), wherein the four-bar linkage (31) comprises a first link (311), a second link (312), a third link (313) and a fourth link (314) which are hinged in sequence and arranged in a ring shape, the driving member (32) is arranged on the suspension mechanism (1) and connected to the four-bar linkage (31), and the seat frame bracket (2) can move relative to the suspension mechanism (1) in a preset direction so that the driving member (32) can drive the four-bar linkage (31) to change its shape.

2. The backrest mechanism according to claim 1, characterized in that: The first connecting rod (311) is fixedly connected to the seat frame bracket (2), and the driving member (32) drives the second connecting rod (312) to rotate around a hinge point between the second connecting rod (312) and the first connecting rod (311).

3. The backrest mechanism according to claim 2, characterized in that: The second connecting rod (312) is hinged to one end of the first connecting rod (311) and one end of the third connecting rod (313) respectively; the fourth connecting rod (314) is located on one side of the second connecting rod (312) and is hinged to one end of the first connecting rod (311) away from the second connecting rod (312) and one end of the third connecting rod (313) away from the second connecting rod (312) respectively.

4. The backrest mechanism according to claim 3, characterized in that: The driving member (32) is a driving rod, one end of which is hinged to the suspension mechanism (1), one end of the second connecting rod (312) is hinged to the third connecting rod (313), and the other end is hinged to the other end of the driving rod, and the middle part of the second connecting rod (312) is hinged to the first connecting rod (311).

5. The backrest mechanism according to any one of claims 1 to 4, characterized in that: The third connecting rod (313) is provided with a first limiting protrusion (3131), and the first limiting protrusion (3131) is located between the second connecting rod (312) and the fourth connecting rod (314); the first connecting rod (311) is provided with a second limiting protrusion (3111), and the second limiting protrusion (3111) is located on a side of the fourth connecting rod (314) away from the second connecting rod (312); Either the first limiting protrusion (3131) or the second limiting protrusion (3111) abuts against the fourth connecting rod (314).

6. A chair frame, comprising a backrest mechanism (3) as claimed in any one of claims 1 to 5, characterized in that: Also includes: Suspension mechanism (1); Seat frame bracket (2); being hinged to the suspension mechanism (1); The seat frame bracket (2) is capable of moving relative to the suspension mechanism (1) along the preset direction, so that the driving member (32) can drive the four-bar linkage (31) to change its shape.

7. The seat iron frame according to claim 6, characterized in that: It also includes a pedal telescopic mechanism (4), which is fixed to the seat frame bracket (2) and includes an extension rod group (41), a main foot pedal (42) and an auxiliary foot pedal assembly (43), and the extension rod group (41) drives the main foot pedal (42) and the auxiliary foot pedal assembly (43) to extend or retract relative to the seat frame bracket (2).

8. The seat iron frame according to claim 7, characterized in that: The stretching rod group (41) includes a first stretching rod (411), a second stretching rod (412), a third stretching rod (413) and a fourth stretching rod (414); the first stretching rod (411) is hinged to the second stretching rod (412); the third stretching rod (413) is hinged to the fourth stretching rod (414); the middle part of the first stretching rod (411) is cross-hinged to the middle part of the fourth stretching rod (414); the first stretching rod (411) and the third stretching rod (413) are respectively hinged to the seat frame bracket (2); the second stretching rod (412) and the fourth stretching rod (414) are respectively hinged to the main footrest (42).

9. The seat iron frame according to claim 8, characterized in that: The auxiliary footrest assembly (43) comprises an auxiliary footrest (431) and an auxiliary connecting rod (432); two ends of the auxiliary connecting rod (432) are respectively hinged to the auxiliary footrest (431) and the main footrest (42); the middle part of the second extension rod (412) is hinged to the main footrest (42); and one end of the second extension rod (412) away from the first extension rod (411) is hinged to the auxiliary footrest (431).

10. The seat iron frame according to claim 9, characterized in that: The suspension mechanism (1) comprises a first rod (11), a second rod (12) and a third rod (13); the first rod (11), the second rod (12), the third rod (13) and the seat frame bracket (2) are hinged end to end in sequence and are arranged to form a first annular four-bar structure; The suspension mechanism (1) further comprises a fourth rod (14), a fifth rod (15), a sixth rod (16) and a seventh rod (17); the middle portion of the fourth rod (14) is hinged to one end of the fifth rod (15); the other end of the fifth rod (15) is hinged to one end of the sixth rod (16); the other end of the sixth rod (16) is hinged to the middle portion of the seventh rod (17); one end of the seventh rod (17) is hinged to one end of the fourth rod (14); the fourth rod (14), the fifth rod (15), the sixth rod (16) and the seventh rod (17) are arranged to form a second annular four-bar structure; The suspension mechanism (1) further comprises a first connecting rod (18) and a second connecting rod (19), wherein the first connecting rod (18) comprises a first connecting support rod (181) and a second connecting support rod (182), wherein one end of the first connecting support rod (181) is hinged to the other end of the fourth rod (14), the other end of the first connecting support rod (181) is hinged to the middle part of the second rod (12), one end of the second connecting support rod (182) is hinged to the middle part of the fourth rod (14), the hinged end of the second rod (12) and the first rod (11) is hinged to the other end of the second connecting support rod (182), one end of the second connecting rod (19) is hinged to the middle part of the sixth rod (16), and the other end of the second connecting rod (19) is hinged to the second rod (12).

11. The seat iron frame according to claim 10, characterized in that: The connecting rod (5) further comprises a connecting rod (5), one end of which is hinged to the third stretching rod (413), the other end of which is hinged to the third rod (13), and the hinge between the connecting rod (5) and the third stretching rod (413) is The distance between the joint and the hinge point between the third extension rod (413) and the seat frame bracket (2) is 22mm-26mm. The distance between the two hinge points at both ends of the third stretching rod (413) is 18cm-22cm.

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