Massage chair

Abstract

The utility model discloses a massage chair, contain: seat frame, be equipped with seat part rack on it, backrest frame, be equipped with backrest rack on it, transition frame, be located between seat frame and backrest frame, and with both respectively rotation cooperation, transition frame is equipped with the transition rack that supplies the walking gear walking of massage machine core, transition rack is located between seat part rack and backrest rack, first waist hole for rotation joint transition frame is seted up on seat frame, and first positioning component that has the positioning both rotation joint position between seat frame and transition frame, and / or, the second waist hole for rotation joint transition frame is seted up on backrest frame, and second positioning component that has the positioning both rotation joint position between backrest frame and transition frame. The massage chair of the present application is more convenient to install.

Description

Technical Field

[0001] This utility model relates to massage equipment technology, specifically, to a massage chair. Background Technology

[0002] Existing massage chairs typically consist of a seat, backrest, and massage mechanism. There are two ways the seat and backrest can be connected. One method involves a fixed connection between the two, with the massage mechanism able to move between the seat and backrest. In this type of massage chair, the backrest cannot move relative to the seat, preventing changes in the user's posture. The other method involves setting the backrest to rotate relative to the seat. However, in this type of massage chair, the massage mechanism can only move within the backrest, resulting in a more limited massage area.

[0003] To address the shortcomings of the aforementioned solutions, existing technology discloses a solution that uses a transition section between the seat and backrest to assist the massage mechanism in moving, thereby achieving a full-body massage. For example, the massage chair disclosed in patent application CN202122460307.8 includes a backrest frame, a seat frame, and a transition frame. One end of the transition frame is hinged to the backrest frame, and the other end of the transition frame is hinged to the seat frame. Each frame is equipped with a rack.

[0004] The technical solution in patent application CN202122460307.8 involves hinge points between the transition frame, backrest frame, and seat frame located on the indexing lines of each rack. These hinge points require precise dimensional control, making parts assembly quite difficult. Therefore, this application is hereby filed. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a massage chair that solves the problem of difficult assembly of parts in existing massage chairs.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A massage chair, comprising: a seat frame with a seat rack disposed thereon; a backrest frame with a backrest rack disposed thereon; a transition frame located between the seat frame and the backrest frame and rotatably engaging with both, wherein the transition frame is provided with a transition rack for the travel gear of the massage mechanism to travel, and the transition rack is located between the seat rack and the backrest rack; the seat frame has a first waist hole for rotatably engaging the transition frame, and a first positioning component is provided between the seat frame and the transition frame to position the two rotatingly engaging; and / or, the backrest frame has a second waist hole for rotatably engaging the transition frame, and a second positioning component is provided between the backrest frame and the transition frame to position the two rotatingly engaging.

[0007] Preferably, the first positioning component includes a first positioning rack and a first positioning gear. The first positioning rack is located outside the seat rack and the transition rack in the left-right direction and corresponds to their positions. The first positioning gear is disposed on the transition frame and meshes with the first positioning rack.

[0008] Preferably, the second positioning component includes a second positioning rack and a second positioning gear. The second positioning rack is located outside the back rack and the transition rack in the left-right direction and corresponds to their positions. The second positioning gear is disposed on the transition frame and meshes with the second positioning rack.

[0009] Preferably, the seat frame is movably mounted on the base frame, and a first drive mechanism is provided therebetween to drive the seat frame and backrest frame to move relative to the base frame (1).

[0010] Preferably, the backrest frame is movably mounted on the base frame, and a drive seat and a first drive mechanism are provided therebetween, wherein the backrest frame as a whole moves relative to the base frame.

[0011] Preferably, a second drive mechanism is provided between the seat frame and the backrest frame to drive the relative movement of the two.

[0012] Preferably, the backrest frame is connected to the seat frame via a pivot rod, the two ends of the pivot rod being rotatably engaged with the seat frame and the backrest frame respectively, and a second drive mechanism is provided between the seat frame and the backrest frame to drive the backrest frame to move relative to the seat frame.

[0013] Due to the adoption of the above technical solutions, this utility model has the following beneficial effects: The massage chair of this application has a first waist hole in the seat frame and a second waist hole in the backrest frame, which can facilitate the assembly of the transition frame with the seat frame and the backrest frame. At the same time, with the cooperation of the first positioning component and the second positioning component, the rotational engagement position of the transition frame can be easily positioned, which can play a role in calibrating the installation position of the transition frame. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of this utility model, and are not intended to limit this utility model.

[0015] Figures 1 to 3 Schematic diagrams of the massage chair of the first embodiment are shown from different perspectives;

[0016] Figure 4 The diagram illustrates the change of the massage chair according to the first embodiment from a seated position to a reclining position.

[0017] Figure 5 A first exploded view of the massage chair according to the first embodiment is shown;

[0018] Figure 6 A second exploded view of the massage chair according to the first embodiment is shown;

[0019] Figure 7 A third exploded view of the massage chair according to the first embodiment is shown;

[0020] Figure 8 An exploded view of the limiting mechanism of the massage chair according to the first embodiment is shown;

[0021] Figure 9 A schematic diagram of the limiting mechanism of the massage chair according to the first embodiment is shown;

[0022] Figure 10 and Figure 11 Schematic diagrams of the massage chair in the second embodiment are shown from different perspectives;

[0023] Figure 12 A first exploded view of the massage chair according to the second embodiment is shown;

[0024] Figure 13 A second exploded view of the massage chair according to the second embodiment is shown.

[0025] Figure label:

[0026] Base frame 1, seat frame 2, backrest frame 3, transition frame 4, support seat 4A, pivot seat 4B, connecting rod 4C, first pin 4D, second pin 4E, first drive mechanism 5, second drive mechanism 6, positioning mechanism 7, first positioning component 7A, second positioning component 7B, limiting mechanism 8, pivot rod T, seat rack P1, backrest rack P2, transition rack P3, first positioning rack M1, first positioning gear N1, second positioning rack M2, second positioning gear N2. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0028] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, features in the following embodiments can be combined with each other.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, features in the following embodiments can be combined with each other.

[0031] [First Embodiment] Combination Figures 1 to 9 In one embodiment, the massage chair of this application includes a base frame 1, a seat frame 2, a backrest frame 3, a transition frame 4, a first drive mechanism 5, a second drive mechanism 6, a positioning mechanism 7, a limiting mechanism 8, and a massage mechanism (not shown). The massage mechanism is, for example, an existing massage mechanism as described in patent application CN202410281566.X, which includes traveling wheels and traveling gears. The massage mechanism is a common massage structure and is not the focus of this application, so it will not be described in detail. For ease of explanation, the X direction in the figures represents the left-right direction, the Y direction represents the front-back direction, and the Z direction represents the up-down direction. Further explanation will follow with reference to the figures.

[0032] The base frame 1 is used to support the seat frame 2 and the backrest frame 3, and arc-shaped guide rails 1A are provided on its left and right sides.

[0033] The seat frame 2, designed to support the user's buttocks, is movably mounted on the base frame 1. Specifically, rollers 2A, which mate with the curved guide rail 1A, are located on both the left and right sides of the seat frame 2. The rollers 2A are positioned within the curved guide rail 1A. The seat frame 2 is equipped with a rack P1 for the movement of the massage mechanism's gears. Figure 6 The base 2 has a first waist hole S1 for rotating and engaging the transition frame 4. It should be understood that the base 2 is not limited to being movably mounted on the base frame 1; for example, it can be adjusted to support the base frame 2 on the base frame 1 via a rocker arm mechanism.

[0034] The backrest frame 3 supports the user's back and is equipped with a backrest rack P2 for the movement of the massage mechanism's gears. In this embodiment, the backrest frame 3 is connected to the seat frame 2 via a pivot rod T, with both ends of the pivot rod T rotatably engaging with the seat frame 2 and the backrest frame 3, respectively. Figure 6 The backrest frame 3 has a second waist hole S2 for rotating and engaging the transition frame 4.

[0035] [Transition Frame] The transition frame 4 is located between the seat frame 2 and the backrest frame 3, and is rotatably engaged with both. The transition frame 4 is equipped with a transition rack P3 for the travel gear of the massage mechanism. The transition rack P3 is located between the seat rack P1 and the backrest rack P2. In this embodiment, the transition frame 4 includes a rack support 4A, a pivot seat 4B, a connecting rod 4C, a first pin 4D, and a second pin 4E. The transition rack P3 is supported on the rack support 4A, which is disposed on the pivot seat 4B. The connecting rod 4C is disposed on the outside of the pivot seat 4B along the left-right direction X. The first pin 4D and the second pin 4E extend along the left-right direction X, connecting the rack support 4A, the pivot seat 4B, and the connecting rod 4C. The first pin 4D passes through the first waist hole S1, allowing the transition frame 4 to rotatably engage with the seat frame 2 via the first pin 4D. The second pin 4E passes through the second waist hole S2, allowing the transition frame 4 to rotate with the backrest frame 3 via the second pin 4E. Compared to a round hole, this application uses a design with a first waist hole S1 and a second waist hole S2, which facilitates the assembly of the transition frame 4 with the seat frame 2 and the backrest frame 3.

[0036] The first drive mechanism 5 is used to drive the seat frame 2 and the backrest frame 3 to move relative to the base frame 1. In this embodiment, the first drive mechanism 5 is installed between the base frame 1 and the seat frame 2. In this embodiment, the first drive mechanism 5 is a slider-type push rod, with its motor end pivotally connected to the base frame 1 and its slider end pivotally connected to the seat frame 2. The first drive mechanism 5 can also be adjusted to be a telescopic push rod.

[0037] The second drive mechanism 6 is used to drive the relative movement of the seat frame 2 and the backrest frame 3. The second drive mechanism 6 is installed between the seat frame 2 and the backrest frame 3. In this embodiment, the second drive mechanism 6 is a telescopic push rod, with its motor end pivotally connected to the seat frame 2 and its telescopic rod end pivotally connected to the backrest frame 3. When its telescopic rod end extends or retracts, it drives the backrest frame 3 to move relative to the seat frame 2.

[0038] [Positioning Mechanism] The positioning mechanism 7 is used to position the transition frame 4 in rotational engagement with the seat frame 2 and backrest frame 3, thus calibrating the installation position of the transition frame 4. Simultaneously, the positioning mechanism 7 maintains the engagement state of the transition rack P3 with the seat rack P1 and backrest rack P2, ensuring that the traveling gears of the massage mechanism always pass between the seat rack P1, backrest rack P2, and transition rack P3. Specifically, combined with... Figure 5In this embodiment, the positioning mechanism 7 includes a first positioning component 7A and a second positioning component 7B. The first positioning component 7A is located between the seat frame 2 and the transition frame 4, and is used to position the two in a rotatable engagement position. The second positioning component 7B is located between the backrest frame 3 and the transition frame 4, and is used to position the two in a rotatable engagement position. The first positioning component 7A includes a first positioning rack M1 and a first positioning gear N1. The first positioning gear N1 is sleeved on the first pin 4D and clamped between the pivot seat 4B and the connecting rod 4C. The first positioning rack M1 is located outside the seat rack P1 and the transition rack P3 in the left-right direction X and corresponds to their positions. The first positioning gear N1 is disposed on the transition frame 4 and meshes with the first positioning rack M1. The second positioning component 7B includes a second positioning rack M2 and a second positioning gear N2. The second positioning gear N2 is sleeved on the second pin 4E and clamped between the pivot seat 4B and the connecting rod 4C. The second positioning rack M2 is located outside the backrest rack P2 and the transition rack P3 in the left-right direction X and corresponds to their positions. The second positioning gear N2 is disposed on the transition frame 4 and meshes with the second positioning rack M2. The parameters of the first positioning rack M1 correspond to the parameters of the seat rack P1 and the transition rack P3. The parameters of the second positioning rack M2 correspond to the parameters of the backrest rack P2 and the transition rack P3. The parameters of the first positioning gear N1 and the second positioning gear N2 correspond to the parameters of the traveling gear of the massage mechanism.

[0039] [Limiting Mechanism] The limiting mechanism 8 is used to prevent the running wheels of the massage mechanism from jumping at the junction of the seat frame 2 and the transition frame 4, and at the junction of the backrest frame 3 and the transition frame 4. Specifically, in this embodiment, the limiting mechanism 8 includes a seat-side pressure strip 8A, a back-side pressure strip 8B, and an elastic element 8C.

[0040] The side pressure strip 8A is mounted on the seat frame 2 to prevent the travel wheels of the massage mechanism from bouncing at the junction of the seat frame 2 and the transition frame 4. Figure 8 and Figure 9 The seat side pressure strip 8A has a seat side sliding groove 8A1, and a seat side limiting member Q1 is provided on the seat side pressure strip 8A. The seat side limiting member Q1 is slidably engaged with the seat side sliding groove 8A1. In this way, the seat side pressure strip 8A and the seat frame 2 are slidably engaged in the extension direction L1 of the seat rack P1.

[0041] The backrest pressure strip 8B is mounted on the backrest frame 3 to prevent the massage mechanism's wheels from bouncing at the junction of the backrest frame 3 and the transition frame 4. Figure 8 and Figure 9 The back side pressure strip 8B has a back side sliding groove 8B1, and a back side limiting member Q2 is provided on the back side pressure strip 8B. The back side limiting member Q2 is slidably engaged with the back side sliding groove 8B1. In this way, the back side pressure strip 8B and the backrest frame 3 are slidably engaged in the extension direction L2 of the backrest rack P2.

[0042] An elastic element 8C is disposed between the seat-side pressure strip 8A and the back-side pressure strip 8B. It applies a first elastic force to the seat-side pressure strip 8A and a second elastic force to the back-side pressure strip 8B. The first elastic force ensures that the seat-side pressure strip 8A always tends to slide towards the transition frame 4, and the second elastic force ensures that the back-side pressure strip 8B always tends to slide towards the transition frame 4. When the seat frame 2 and backrest frame 3 rotate relative to the transition frame 4, causing the gap between the transition frame 4 and the seat frame 2 and backrest frame 3 to increase, the seat-side pressure strip 8A and back-side pressure strip 8B can slide elastically under the action of the elastic force. This allows it to adaptively compensate for the changed gap between the transition frame 4 and the seat frame 2 and backrest frame 3, enabling the massage mechanism to move stably at the junction of the transition frame 4 and the seat frame 2 and backrest frame 3. In this embodiment, the elastic element 8C is a spring.

[0043] The above is a detailed description of the massage chair according to the first embodiment of this application. It should be understood that this application may also have other modified designs.

[0044] [Second Embodiment] In the first embodiment, the seat frame 2 is movably mounted on the base frame 1, the first drive mechanism 5 is installed between the base frame 1 and the seat frame 2, and the second drive mechanism 6 drives the backrest frame 3 to rotate relative to the seat frame 2. Unlike the above configuration of the first embodiment, combined with... Figures 10 to 13 In the second embodiment, the backrest frame 3 is movably mounted on the base frame 1 (rollers that cooperate with the base frame 1 are provided on the left and right sides of the backrest frame 3). The first drive mechanism 5 is installed between the base frame 1 and the backrest frame 3. The first drive mechanism 5 is a slider-type push rod, with its motor end pivotally connected to the base frame 1 and its slider end pivotally connected to the backrest frame 3. The first drive mechanism 5 can also be adjusted to be a telescopic push rod. In the second embodiment, the second drive mechanism 6 drives the seat frame 2 to move relative to the backrest frame 3. The second drive mechanism 6 is a telescopic push rod, with its motor end pivotally connected to the backrest frame 3 and its telescopic rod end pivotally connected to the seat frame 2. When its telescopic rod end extends or retracts, it drives the seat frame 2 to move relative to the backrest frame 3. It should be understood that the backrest frame 3 being movably mounted on the base frame 1 is not limited to this; for example, it can be adjusted to support the backrest frame 3 on the base frame 1 through a swing arm mechanism. In the second embodiment, other features not mentioned can be the same as in the first embodiment and will not be described again.

[0045] [Third Embodiment] In the first embodiment, the seat-side pressure strip 8A and the back-side pressure strip 8B are subjected to elastic force by the same elastic element 8C. In the third embodiment, two elastic elements can be designed to apply elastic force to the seat-side pressure strip 8A and the back-side pressure strip 8B respectively. One elastic element can be disposed between the seat-side pressure strip 8A and the transition frame 4, and the other elastic element can be disposed between the back-side pressure strip 8B and the transition frame 4. In the third embodiment, other characteristics not mentioned are the same as in the first or second embodiment, and will not be described again.

[0046] [Fourth Embodiment] Unlike the first embodiment, which includes both seat side pressure strip 8A and back side pressure strip 8B, the fourth embodiment may only include seat side pressure strip 8A. That is, this application also provides a massage chair, comprising: a seat frame 2, on which a seat rack P1 is disposed for the travel gear of the massage mechanism; a backrest frame 3, on which a back rack P2 is disposed for the travel gear of the massage mechanism; a transition frame 4, on which a transition rack P3 is disposed for the travel gear of the massage mechanism, the transition frame 4 being located between the seat frame 2 and the backrest frame 3 and rotatably engaging with both, the transition rack P3 being located between the seat rack P1 and the back rack P2; a seat side pressure strip 8A, disposed on the seat frame 2, for preventing the travel wheel of the massage mechanism from jumping at the junction of the seat frame 2 and the transition frame 4; wherein, the seat side pressure strip 8A is configured to: slide engage with the seat frame 2 in the extension direction L1 of the seat rack P1, and be applied a first elastic force so that it always has a sliding tendency toward the transition frame 4. An elastic element for applying a first elastic force to the seat-side pressure strip 8A can be disposed between the seat-side pressure strip 8A and the transition frame 4. Other characteristics not mentioned in the fourth embodiment are the same as those in the first or second embodiments and will not be described further.

[0047] [Fifth Embodiment] Unlike the first embodiment, which includes both seat side pressure strip 8A and back side pressure strip 8B, the fifth embodiment may only include back side pressure strip 8B. That is, this application also provides a massage chair, comprising: a seat frame 2, on which a seat rack P1 is disposed for the travel gear of the massage mechanism; a backrest frame 3, on which a back rack P2 is disposed for the travel gear of the massage mechanism; a transition frame 4, which is located between the seat frame 2 and the backrest frame 3 and is rotatably engaged with both, the transition frame 4 being disposed with a transition rack P3 for the travel gear of the massage mechanism, the transition rack P3 being located between the seat rack P1 and the back rack P2; and a backrest pressure strip 8B, disposed on the backrest frame 3, for preventing the travel wheel of the massage mechanism from jumping at the junction of the backrest frame 3 and the transition frame 4; wherein, the backrest pressure strip 8B is configured to slide in engagement with the backrest frame 3 in the extension direction L2 of the back rack P2, and is subjected to a second elastic force that always gives it a tendency to slide toward the transition frame 4. An elastic element for applying a second elastic force to the back side pressure strip 8B can be disposed between the back side pressure strip 8B and the transition frame 4. Other features not mentioned in the fifth embodiment are the same as those in the first or second embodiment and will not be described again.

[0048] [Sixth Embodiment] Based on the first embodiment, one of the seat-side pressure strip 8A and the back-side pressure strip 8B can be configured to slide elastically. Other characteristics not mentioned in the sixth embodiment can be the same as those in the first or second embodiment, and will not be described again.

[0049] [Seventh Embodiment] Based on the first embodiment, it can be adjusted to have only one waist hole and one positioning component.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A massage chair, comprising: A seat frame (2) on which a seat rack (P1) is mounted; Backrest frame (3), on which a backrest rack (P2) is mounted; A transition frame (4) is located between the seat frame (2) and the backrest frame (3) and is rotatably engaged with both of them. The transition frame (4) is equipped with a transition rack (P3) for the travel gear of the massage mechanism to travel. The transition rack (P3) is located between the seat rack (P1) and the backrest rack (P2). Its features are, The base (2) has a first waist hole (S1) for rotatably engaging the transition frame (4), and the base (2) and the transition frame (4) have a first positioning component (7A) for positioning their rotatable engagement position; and / or, The backrest frame (3) has a second waist hole (S2) for rotating and engaging the transition frame (4), and the backrest frame (3) and the transition frame (4) have a second positioning component (7B) for positioning the rotating engagement position of the two.

2. The massage chair according to claim 1, characterized in that, The first positioning component (7A) includes a first positioning rack (M1) and a first positioning gear (N1). The first positioning rack (M1) is located outside the seat rack (P1) and the transition rack (P3) in the left-right direction and corresponds to their positions. The first positioning gear (N1) is disposed on the transition frame (4) and meshes with the first positioning rack (M1).

3. The massage chair according to claim 1, characterized in that, The second positioning component (7B) includes a second positioning rack (M2) and a second positioning gear (N2). The second positioning rack (M2) is located outside the back rack (P2) and the transition rack (P3) in the left-right direction and corresponds to their positions. The second positioning gear (N2) is disposed on the transition frame (4) and meshes with the second positioning rack (M2).

4. The massage chair according to claim 1, characterized in that, The seat frame (2) is movably mounted on the base frame (1), and a first drive mechanism (5) is provided therebetween to drive the seat frame (2) and the backrest frame (3) to move relative to the base frame (1).

5. The massage chair according to claim 1, characterized in that, The backrest frame (3) is movably mounted on the base frame (1), and a drive seat frame (2) and a first drive mechanism (5) are provided therebetween, in which the backrest frame (3) moves relative to the base frame (1).

6. The massage chair according to claim 4 or 5, characterized in that, A second drive mechanism (6) is provided between the seat frame (2) and the backrest frame (3) to drive the relative movement of the two.

7. The massage chair according to claim 1, characterized in that, The backrest frame (3) is connected to the seat frame (2) via a pivot rod (T), and the two ends of the pivot rod (T) are rotatably engaged with the seat frame (2) and the backrest frame (3) respectively.

8. The massage chair according to claim 2, characterized in that, The transition frame (4) includes a rack support (4A), a pivot seat (4B), a connecting rod (4C), a first pin (4D), and a second pin (4E). The transition rack (P3) is supported on the rack support (4A), which is positioned on the pivot seat (4B). The connecting rod (4C) is located on the outside of the pivot seat (4B) along the left-right direction (X). The first pin (4D) and the second pin (4E) extend along the left-right direction (X) and are connected... The frame includes a rack and pinion support (4A), a pivot support (4B), and a connecting rod (4C). The first pin (4D) passes through the first waist hole (S1), allowing the transition frame (4) to rotate with the seat frame (2) via the first pin (4D). The second pin (4E) passes through the second waist hole (S2), allowing the transition frame (4) to rotate with the backrest frame (3) via the second pin (4E). The first positioning gear (N1) is sleeved on the first pin (4D) and clamped between the pivot support (4B) and the connecting rod (4C).

9. The massage chair according to claim 2, characterized in that, The transition frame (4) includes a rack support (4A), a pivot seat (4B), a connecting rod (4C), a first pin (4D), and a second pin (4E). The transition rack (P3) is supported on the rack support (4A), which is positioned on the pivot seat (4B). The connecting rod (4C) is located on the outside of the pivot seat (4B) along the left-right direction (X). The first pin (4D) and the second pin (4E) extend along the left-right direction (X) and are connected... The frame includes a rack and pinion support (4A), a pivot support (4B), and a connecting rod (4C). The first pin (4D) passes through the first waist hole (S1), allowing the transition frame (4) to rotate with the seat frame (2) via the first pin (4D). The second pin (4E) passes through the second waist hole (S2), allowing the transition frame (4) to rotate with the backrest frame (3) via the second pin (4E). The second positioning gear (N2) is sleeved on the second pin (4E) and clamped between the pivot support (4B) and the connecting rod (4C).

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