Bed for old people

Abstract

The utility model relates to the field of life auxiliary equipment, in particular to a pension bed which comprises supporting legs, a bed frame arranged on the supporting legs, a bed board assembly arranged on the bed frame and an adjusting assembly used for adjusting the bed board assembly, the bed board assembly is composed of a plurality of sections of structures, and the sections of bed board structures are hinged together. Wherein the adjusting assembly can be used for supporting and adjusting each section of bed board structure. The inclination angle of each section of bed board structure can be controlled, when an old person lies on the bed board assembly, the inclination angle of each section of bed board structure can be adjusted through the adjusting assembly, then the prone position is adjusted, and the comfort degree of the old person lying on the bed is increased.

Description

Technical Field

[0001] This utility model relates to the field of living assistance equipment, and in particular to a nursing home bed. Background Art

[0002] As the physical functions of the elderly gradually decline, their arm and waist strength decreases. Considering the physical condition and lifestyle of the elderly, it is necessary to design a special elderly care bed to alleviate their discomfort when lying in bed.

[0003] Currently, a Chinese utility model patent application with publication number CN213666279U and publication date of July 13, 2021, proposes a nursing home bed, which includes a bed frame and a bed board set on the bed frame. The bed board includes a back panel, a seat panel and a leg panel distributed from front to back. The seat panel is fixedly connected to the bed frame, the back panel is connected to the bed frame through a rotation drive mechanism, there is a gap between the back panel and the seat panel, and the front end of the leg panel is hinged to the rear end of the seat panel.

[0004] In use, the back of the back panel is provided with a connecting plate extending in the front-to-back direction. The rotation drive mechanism includes a first push rod motor, two first connecting rods, and two second connecting rods. The body of the first push rod motor is rotatably mounted on the bed frame. The push rod of the first push rod motor is axially connected to the back of the back panel. One end of the first connecting rod is axially connected to the bed frame, and the other end of the first connecting rod is axially connected to one end of the connecting plate. One end of the second connecting rod is axially connected to the bed frame, and the other end of the second connecting rod is axially connected to the other end of the connecting plate. The first connecting rods and the second connecting rods cooperate to control the direction and angle of the back panel rotation, ensuring that there is always a gap between the back panel and the seat plate.

[0005] Regarding the aforementioned technologies, when elderly people lie on nursing beds, their backs and buttocks are constantly compressed, which can easily lead to discomfort in the back and buttocks, and even cause blood clots in the back or buttocks, affecting their physical condition. Utility Model Content

[0006] In order to alleviate the pressure on the back and hips of the elderly when lying in bed and improve the comfort of the elderly care bed, this utility model provides an elderly care bed.

[0007] This utility model provides a nursing home bed, which adopts the following technical solution:

[0008] An elderly care bed includes support legs, a bed frame disposed above the support legs, and a bed board assembly disposed on the bed frame;

[0009] It also includes an adjustment assembly, which includes a first lifting rod, a second lifting rod, a first support rod, and a second support rod. The fixed ends of the first lifting rod and the second lifting rod are arranged on the bed frame along the length direction of the bed frame. One end of the first support rod is slidably arranged on the bed frame, and the other end is rotatably connected to the bed board assembly. One end of the second support rod is slidably arranged on the bed frame, and the other end is rotatably connected to the bed board assembly.

[0010] The bed frame is provided with a first drive and a second drive. One end of the first support rod is slidably disposed on the bed frame and is connected to the first drive. One end of the second support rod is slidably disposed on the bed frame and is connected to the second drive.

[0011] The bed board assembly includes a backrest, a first lifting plate, a second lifting plate, a thigh plate, and a calf plate. The first lifting plate is fixedly mounted on the movable end of the first lifting rod, and the second lifting plate is fixedly mounted on the movable end of the second lifting rod. One side of the backrest is rotatably mounted on the side of the first lifting plate away from the second lifting plate, and the other side of the backrest is rotatably connected to the other end of the first support rod. One side of the thigh plate is rotatably mounted on the first lifting plate, and the other side is rotatably mounted on the second lifting plate. The calf plate is rotatably mounted on the side of the second lifting plate away from the first lifting plate, and the other side of the calf plate is rotatably connected to the other end of the second support rod.

[0012] Position compensation structures are provided at the positions where the thigh plate connects to the first lifting plate and at the positions where the thigh plate connects to the second lifting plate.

[0013] By adopting the above technical solution, controlling the first and second lifting rods can respectively drive the first and second lifting plates to move, thereby adjusting the tilt angle of the thigh board. Controlling the first support rod with the first drive can raise or lower the backrest, thus adjusting its tilt angle. Controlling the second support rod with the second drive can raise or lower the calf board, thus adjusting its tilt angle. Lowering the first lifting plate, raising the second lifting plate, supporting the backrest, and lowering the calf board creates a certain tilt arc in the bed assembly. This allows the elderly person lying on the bed assembly to reduce pressure on their back or buttocks and improve comfort by adjusting the tilt angle. Simultaneously, raising the backrest to its highest position and lowering the calf board to its lowest position creates a seat-like shape, helping the elderly person transition from a lying to a sitting position and assisting in getting up. Finally, controlling the simultaneous raising or lowering of the first and second lifting plates adjusts the height of the bed assembly, increasing the applicability of this elderly care bed.

[0014] Optionally, the bed frame is provided with a height-adjustable handrail at the top, and the height-adjustable handrail is provided at two edges of the bed frame along the length of the bed frame.

[0015] By adopting the above technical solution, the adjustable handrails can be raised when the elderly person is lying on the nursing bed to prevent them from rolling off. The handrails can be lowered when they need to get up from the side of the bed or retrieve something from the bedside. This adjustable handrail design increases the safety of the nursing bed.

[0016] Optionally, the liftable handrail is provided with control buttons, which are located on the liftable handrail at positions corresponding to the first lifting plate. The control buttons are electrically connected to the first lifting rod, the second lifting rod, the first drive, the second drive, and the liftable handrail.

[0017] By adopting the above technical solution, the control buttons are set on the height-adjustable armrests corresponding to the first lifting plate, so that the elderly can easily adjust the tilt angle of the bed board assembly by controlling the buttons when lying on the nursing bed, thus increasing the portability of the nursing bed.

[0018] Optionally, the liftable handrail is provided with a protective shell, which covers the outside of the control button. An elastic element is provided between the protective shell and the liftable handrail, and the elastic element has a tendency to close the protective shell.

[0019] By adopting the above technical solution, when adjusting the tilt angle of the bed board assembly using the control buttons, the protective cover needs to be opened first. After using the control buttons, the protective cover will automatically close under the action of the elastic element. This protective cover design reduces the number of accidental presses of the control buttons and increases their service life.

[0020] Optionally, the first support rod includes a pivot portion and a connecting rod portion. The pivot portion is rotatably disposed on the side of the back plate near the ground. One end of the connecting rod portion is fixedly connected to the middle position of the pivot portion, and the other end is connected to the first drive transmission.

[0021] By adopting the above technical solution, the first drive can drive the first support rod to rotate. When the first support rod supports the back panel, the first drive transmits power to the connecting rod, which supports multiple positions of the back panel through the rotating shaft. This increases the stability of the back panel, and thus increases the stability of the bed board assembly.

[0022] Optionally, the first drive includes a first motor fixedly mounted on the bed frame, a first lead screw rotatably mounted on the bed frame, and a first lead screw nut cooperating with the first lead screw. The first lead screw nut is rotatably mounted at the end of the connecting rod portion away from the rotating shaft portion. The first lead screw is disposed below the bed board assembly along the length direction of the bed frame. The first lead screw is drively connected to the output shaft of the first motor.

[0023] By adopting the above technical solution, when the first lead screw rotates, the first lead screw nut moves along the direction of the first lead screw. The first lead screw is rotatably connected to the connecting rod of the first support rod. When the first lead screw nut moves, it lifts the first support rod, thereby lifting the back plate and adjusting the tilt angle of the back plate. Thus, when the first support rod is driven by the first lead screw, due to the self-locking property of the lead screw transmission system, even if the motor loses power or other faults occur during the driving process, the back plate can still be self-locked at the current tilt angle. This improves the stability of the first support rod, reduces the safety hazards caused by the first support rod failing to support the back plate during power failure, and enhances the safety of the elderly care bed.

[0024] Optionally, the second drive includes a second motor fixedly mounted on the bed frame, a second lead screw rotatably mounted on the bed frame, and a second lead screw nut cooperating with the second lead screw. The second lead screw is mounted on the bed frame on the side near the lower leg plate, and the second lead screw nut is rotatably mounted at the end of the second support rod away from the bed board assembly.

[0025] By adopting the above technical solution, when the second lead screw rotates, the second lead screw nut can slide along the direction of the second lead screw. The second lead screw nut is rotatably connected to the second support rod, which can drive the second support rod and thus adjust the tilt angle of the lower leg plate. When the lower leg plate is supported and adjusted using a lead screw assembly, the self-locking property of the lead screw drive can also be used to improve the stability of the second support rod, thereby improving the safety of the elderly care bed.

[0026] Optionally, the position compensation structure includes slots respectively disposed on the first lifting plate and the second lifting plate, and a limiting link disposed in the slot. The limiting link is slidably disposed in the slot. The thigh plate is rotatably connected to the slot on the first lifting plate and the thigh plate is rotatably connected to the slot on the second lifting plate through the limiting link. The limiting link and the slot are in contact through a bearing.

[0027] By adopting the above technical solution, when the first lifting plate and the second lifting plate move, the first support plate and the second support plate can only move in the vertical direction. The thigh plate is connected to the first support plate and the second support plate and slides in the slot through the pin to compensate for displacement. It can play a linkage role and also play a support role. At the same time, a bearing is fixedly installed on the outer circumference of the pin to reduce the friction between the pin and the inner wall of the slot.

[0028] In summary, this utility model has at least one of the following beneficial technical effects:

[0029] By setting the first lifting rod and the second lifting rod to support the first lifting plate and the second lifting plate respectively, the tilt angle of the back board, thigh board and calf board can be adjusted by adjusting the height of the first lifting plate and the second lifting plate, thereby adjusting the lying posture of the elderly on the nursing bed and reducing the pressure on the elderly's back or buttocks, thus improving the comfort of the nursing bed.

[0030] By combining the first lifting rod, the second lifting rod, the first support rod, and the second support rod, the height of the elderly care bed can be adjusted, increasing its usability. On the other hand, the elderly care bed can also be adjusted to a sitting position to help the elderly get up from the bed.

[0031] By setting up a screw drive system to drive the first and second support rods, the self-locking property of the screw drive can be used to increase the stability of the first and second support rods, reduce the safety hazards caused by the back panel or lower leg plate suddenly falling after losing support, and increase the safety of the elderly care bed. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the flat state of an embodiment of this utility model;

[0033] Figure 2 This is a schematic diagram of the tilted state of an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the sitting posture of an embodiment of this utility model;

[0035] Figure 4 This is a schematic diagram of the lying position of this utility model embodiment from another perspective;

[0036] Figure 5 yes Figure 1 A magnified view of part I in the middle section.

[0037] Explanation of reference numerals in the attached drawings: 1. Support leg; 2. Bed frame; 21. First drive; 211. First motor; 212. First lead screw; 213. First lead screw nut; 22. Second drive; 221. Second motor; 222. Second lead screw; 223. Second lead screw nut; 23. Adjustable armrest; 24. Control button; 25. Protective shell; 3. Bed board assembly; 31. Backrest; 32. First lifting plate; 33. Second lifting plate; 34. Thigh plate; 35. Lower leg plate; 36. Position compensation structure; 361. Groove; 362. Limiting link; 4. Adjustment assembly; 41. First lifting rod; 42. Second lifting rod; 43. First support rod; 431. Rotating shaft; 432. Connecting rod; 44. Second support rod. Detailed Implementation

[0038] The following combination Figures 1 to 5 The present invention will be described in further detail below.

[0039] This utility model discloses an elderly care bed. (Refer to...) Figures 1 to 3 A type of elderly care bed mainly includes support legs 1, a bed frame 2 mounted on the support legs 1, a bed board assembly 3 mounted on the bed frame 2, and an adjustment component 4 for adjusting the bed board assembly 3. The bed board assembly 3 is composed of multiple sections, each section of the bed board structure is hinged together, and the adjustment component 4 can support and adjust each section of the bed board structure separately, thereby controlling the tilt angle of each section of the bed board structure. When the elderly lie on the bed board assembly 3, they can adjust the tilt angle of each section of the bed board structure through the adjustment component 4, thereby adjusting their lying posture and increasing the comfort of the elderly lying in bed.

[0040] Reference Figures 1 to 3 The bed frame 2 is equipped with support legs 1 at the bottom. The bed frame 2 includes support frames on both sides and connecting rods between the two support frames. The support frames on both sides are equipped with liftable handrails 23. The liftable handrails 23 are connected to the support frames by electric push rods. When the liftable handrails 23 are raised, they can provide protection for the elderly lying in bed. When the liftable handrails 23 are lowered, they can make it easier for the elderly to get up from the side of the bed or to get things.

[0041] Reference Figure 4A first drive 21 is provided on the connecting rod located in the middle of the support frame. The first drive 21 includes a first motor 211, a first lead screw 212, and a first lead screw nut 213. The first motor 211 is fixedly mounted on the side of the connecting rod near the ground by a welded base. One end of the first lead screw 212 is fixedly connected to the output shaft of the first motor 211, and the other end of the first lead screw 212 is rotatably connected to the bed frame 2 by a bearing. The first lead screw nut 213 is sleeved on the first lead screw 212. When the first lead screw 212 rotates, the first lead screw nut 213 can move along the direction of the first lead screw 212.

[0042] Reference Figures 2 to 4 A second drive 22 is provided on one support frame of the bed frame 2. The second drive 22 includes a second motor 221, a second lead screw 222, and a second lead screw nut 223. The second motor 221 is fixedly mounted on the support frame. One end of the second lead screw 222 is connected to the output shaft of the second motor 221, and the other end of the second lead screw 222 is connected to the support frame through a bearing. The second lead screw nut 223 is sleeved on the second lead screw 222. To prevent people from touching the second lead screw 222 when passing by, a guard plate is also provided on the support frame. The guard plate covers the end of the second lead screw 222 near the outside of the bed. When the second motor 221 drives the second lead screw 222 to rotate, the second lead screw nut 223 will move on the second lead screw 222. A cylindrical slide rod is provided on the other support frame of the bed frame 2. The position of the cylindrical slide rod corresponds to the position of the second lead screw 222.

[0043] Reference Figure 1 and Figure 5 The bed board assembly 3 includes a backrest 31, a first lifting plate 32, a thigh plate 34, a second lifting plate 33, and a lower leg plate 35 connected in sequence. The connection between the backrest 31 and the first lifting plate 32, and the connection between the second lifting plate 33 and the lower leg plate 35, are all connected by rotating rods. The connection between the first lifting plate 32 and the thigh plate 34, and the connection between the second lifting plate 33 and the thigh plate 34, are provided with position compensation structures 36. The position compensation structure 36 consists of slots 361 at both ends of the first lifting plate 32, the second lifting plate 33, and the thigh plate 34, and a limiting link 362 passing through the slots 361. The limiting link 362 can move in the slots 361, thereby allowing a cylindrical rotating shaft link to pass through the slots 361 at both ends of the first lifting plate 32, the second lifting plate 33, and the thigh plate 34 to perform position compensation at the connection between the first lifting plate 32 and the thigh plate 34, and the connection between the second lifting plate 33 and the thigh plate 34.

[0044] Reference Figure 3 and Figure 4The adjusting assembly 4 includes a first lifting rod 41, a second lifting rod 42, a first support rod 43, and a second support rod 44. The first lifting rod 41 and the second lifting rod 42 are electric push rods. The fixed ends of the electric push rods are vertically fixed to a connecting rod used to connect the support frames on both sides. The movable ends of the electric push rods are respectively fixedly connected to the ground-facing ends of the first lifting plate 32 and the second lifting plate 33. The first support rod 43 includes a connecting rod portion 432 and a rotating shaft portion 431. One end of the connecting rod portion 432 is fixedly positioned in the middle of the rotating shaft portion 431, and the other end of the connecting rod portion 432 has a circular limiting hole. A first lead screw nut 213 is rotatably positioned in the circular limiting hole and connected to the first support rod 44 via a pin. The outer side of the lead screw nut 213 is limited. Two ear plates are fixedly installed on the side of the back plate 31 near the ground. The ear plates have circular holes. The two ends of the rotating shaft 431 are rotatably connected to the two ear plates through pins. Two ear plates are fixedly installed on the side of the lower leg plate 35 near the ground. The ear plates have circular holes. Two second support rods 44 are provided. One end of the second support rod 44 is rotatably connected to one of the ear plates through a pin. The other end is provided with a circular limiting hole. A rotating shaft is set in the circular limiting hole and fixedly connected to the second lead screw nut 223. One end of the other second support rod 44 is rotatably connected to the other ear plate through a pin. The other end is slidably connected to a cylindrical slide rod on the other side of the support frame.

[0045] Reference Figure 1 The adjustable armrest 23 is also equipped with control buttons 24, which are electrically connected to the first lifting rod 41, the second lifting rod 42, the first drive 21, and the second drive 22. The first lifting rod 41, the second lifting rod 42, the first drive 21, and the second drive 22 can be controlled by the control buttons 24 to adjust the tilt angle of the bed board assembly 3. In order to prevent accidental touch of the control buttons 24, a protective shell 25 is also provided on the outside of the control buttons 24. One side of the protective shell 25 is rotatably connected to the adjustable armrest 23 by a hinge. In order for the protective shell 25 to close automatically, an elastic element is provided on the hinge. The elastic element is a torsion spring. The torsion spring can automatically close the protective shell 25 under the action of the elastic force.

[0046] The implementation principle of the elderly care bed in this embodiment of the utility model is as follows: the first lifting rod 41 can drive the first lifting plate 32 to move in the vertical direction, and the second lifting rod 42 can drive the second lifting plate 33 to rotate in the vertical direction. When the first lifting plate 32 and the second lifting plate 33 are relatively displaced in the vertical direction, the position compensation structure 36 can perform position compensation so that the thigh plate 34 can rotate normally relative to the first lifting plate 32 and the second lifting plate 33.

[0047] When the first lead screw 212 drives the first lead screw nut 213 to move away from the first motor 211, the first support rod 43 rotates relative to the first lead screw nut 213 and the back plate 31, and lifts the back plate 31 upwards; conversely, it lowers the back plate 31. When the second lead screw 222 drives the second lead screw nut 223 to move closer to the second motor 221, the second support rod 44 rotates relative to the second lead screw nut 223 and the lower leg plate 35, and pulls the lower leg plate 35 downwards; conversely, it lifts the lower leg plate 35.

[0048] When lying on the nursing bed, the first lifting board 32 can be raised, the second lifting board 33 can be lowered, the back board 31 can be raised, and the calf board 35 can be lowered, forming a lying position with the buttocks and calves in a low position and the chest and knee joints in a high position. This reduces pressure on the buttocks, waist and chest, promotes blood flow in the back and legs, and increases the comfort of the lying position.

[0049] When getting up, the first lifting plate 32 and the second lifting plate 33 are lowered to the lowest position, the backrest 31 is further raised to form an angle close to the ground, and the lower leg plate 35 is lowered to an angle close to the ground near the foot of the bed, so that the bed board assembly 3 is in a shape close to a sitting posture, to help the elderly get up.

[0050] To accommodate different heights of elderly people, the first lifting plate 32 and the second lifting plate 33 can be raised or lowered simultaneously, and the first drive 21 and the second drive 22 can be controlled to work in coordination with the first lifting plate 32 and the second lifting plate 33 to adjust the overall height of the bed board assembly 3.

[0051] In summary, this utility model, through the cooperation of the first lifting rod 41, the second lifting rod 42, the first support rod 43, and the second support rod 44, can adjust the tilt angle of the bed board assembly 3, allowing it to be adjusted to accommodate the elderly person's lying posture and increase adaptability; it can adjust the height of the elderly care bed, increasing its usability; it can adjust the elderly care bed to a sitting mode, assisting the elderly person in getting up from the bed; at the same time, it utilizes the self-locking property of the screw drive assembly to increase the stability of the support for the bed board assembly 3; and by setting control buttons 24, it allows the elderly person to control the posture of the bed board assembly 3 themselves, improving the convenience of use.

[0052] The above are all preferred embodiments of this utility model, and are not intended to limit the scope of protection of this utility model. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this utility model should be covered within the scope of protection of this utility model.

Claims

1. A nursing home bed, comprising support legs (1), a bed frame (2) disposed above the support legs (1), and a bed board assembly (3) disposed on the bed frame (2), characterized in that: It also includes an adjustment component (4), which includes a first lifting rod (41), a second lifting rod (42), a first support rod (43), and a second support rod (44). The fixed ends of the first lifting rod (41) and the second lifting rod (42) are arranged on the bed frame (2) along the length direction of the bed frame (2). One end of the first support rod (43) is slidably arranged on the bed frame (2), and the other end is rotatably connected to the bed board assembly (3). One end of the second support rod (44) is slidably arranged on the bed frame (2), and the other end is rotatably connected to the bed board assembly (3). The bed frame (2) is provided with a first drive (21) and a second drive (22). One end of the first support rod (43) is slidably disposed on the bed frame (2) and is connected to the first drive (21) in a transmission connection. One end of the second support rod (44) is slidably disposed on the bed frame (2) and is connected to the second drive (22) in a transmission connection. The bed board assembly (3) includes a backrest (31), a first lifting plate (32), a second lifting plate (33), a thigh plate (34), and a calf plate (35). The first lifting plate (32) is fixedly mounted on the movable end of the first lifting rod (41), and the second lifting plate (33) is fixedly mounted on the movable end of the second lifting rod (42). One side of the backrest (31) is rotatably mounted on the side of the first lifting plate (32) away from the second lifting plate (33), and the other side of the backrest (31) is rotatably connected to the other end of the first support rod (43). One side of the thigh plate (34) is rotatably mounted on the first lifting plate (32), and the other side is rotatably mounted on the second lifting plate (33). The calf plate (35) is rotatably mounted on the side of the second lifting plate (33) away from the first lifting plate (32), and the other side of the calf plate (35) is rotatably connected to the other end of the second support rod (44). Position compensation structures (36) are provided at the positions where the thigh plate (34) is connected to the first lifting plate (32) and at the positions where the thigh plate (34) is connected to the second lifting plate (33).

2. The elderly care bed according to claim 1, characterized in that: A height-adjustable armrest (23) is provided above the bed frame (2), and the height-adjustable armrest (23) is provided at the two edges of the bed frame (2) along the length direction of the bed frame (2).

3. The elderly care bed according to claim 2, characterized in that: The liftable handrail (23) is provided with a control button (24). The control button (24) is located on the liftable handrail (23) at a position corresponding to the first lifting plate (32). The control button (24) is electrically connected to the first lifting rod (41), the second lifting rod (42), the first drive (21), the second drive (22) and the liftable handrail (23).

4. The elderly care bed according to claim 3, characterized in that: The liftable handrail (23) is provided with a protective shell (25), which covers the outside of the control button (24). An elastic element is provided between the protective shell (25) and the liftable handrail (23), and the elastic element has a tendency to close the protective shell (25).

5. A nursing home bed according to any one of claims 1-4, characterized in that: The first support rod (43) includes a pivot (431) and a connecting rod (432). The pivot (431) is rotatably disposed on the side of the back plate (31) near the ground. One end of the connecting rod (432) is fixedly connected to the middle position of the pivot (431), and the other end is connected to the first drive (21) for transmission.

6. The elderly care bed according to claim 5, characterized in that: The first drive (21) includes a first motor (211) fixedly mounted on the bed frame (2), a first lead screw (212) rotatably mounted on the bed frame (2), and a first lead screw nut (213) cooperating with the first lead screw (212). The first lead screw nut (213) is rotatably mounted at one end of the connecting rod (432) away from the rotating shaft (431). The first lead screw (212) is mounted below the bed board assembly (3) along the length direction of the bed frame (2). The first lead screw (212) is connected to the output shaft of the first motor (211) via a transmission.

7. A nursing home bed according to any one of claims 1-4, characterized in that: The second drive (22) includes a second motor (221) fixedly mounted on the bed frame (2), a second lead screw (222) rotatably mounted on the bed frame (2), and a second lead screw nut (223) cooperating with the second lead screw (222). The second lead screw (222) is mounted on the bed frame (2) on the side near the lower leg plate (35), and the second lead screw nut (223) is rotatably mounted at the end of the second support rod (44) away from the bed board assembly (3).

8. A nursing home bed according to any one of claims 1-4, characterized in that: The position compensation structure (36) includes slots (361) respectively disposed on the first lifting plate (32) and the second lifting plate (33) and a limiting link (362) disposed in the slots (361). The limiting link (362) is slidably disposed in the slots (361). The thigh plate (34) is rotatably connected to the slots (361) on the first lifting plate (32) and the thigh plate (34) is rotatably connected to the slots (361) on the second lifting plate (33) through the limiting link (362). The limiting link (362) and the slots (361) are in contact through bearings.

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