Rehabilitation walking aid for orthopedics department

Abstract

The invention discloses an orthopedic rehabilitation walking aid, and belongs to the field of walking aids, the orthopedic rehabilitation walking aid comprises a frame, a cushion is fixed on the top of the frame, a handrail is fixed on the frame, columns are symmetrically fixed on the frame, a support frame is fixed between the two columns, and the orthopedic rehabilitation walking aid further comprises a standing mechanism and a lifting mechanism, the pushing device is used for applying upward pushing force to a patient when the patient gets up; the turnover mechanism is used for applying outward ejection force to the buttocks of the patient when the patient gets up. Through the arrangement of the standing mechanism, when a patient needs to stand up, upward thrust can be applied to the patient, the patient can stand up conveniently, meanwhile, a circular gear and rectangular rack meshing structure can drive a supporting plate to turn outwards in the lifting process of a lifting frame, so that the supporting plate can apply ejection force to the hip of the patient, the patient can stand up conveniently, and the patient can stand up conveniently. And meanwhile, through meshing of a circular gear and a rectangular rack, it can be ensured that the two sets of electric push rods drive the lifting frame and the two sides of the supporting plate to synchronously move upwards.

Description

Technical Field

[0001] The present invention relates to the technical field of walkers, and in particular to an orthopedic rehabilitation walker. Background Art

[0002] During orthopedic diseases or postoperative rehabilitation, walkers are key auxiliary devices to help patients regain the ability to stand and walk. Their safety and functionality directly affect the patient's recovery process. For patients with lower limb fractures, joint replacement surgery or lumbar spine injuries, the basic action of getting up from a sitting position is often challenging. Because the injured area has not yet fully healed, it is difficult for patients to independently control the angle and strength of force when getting up. If they force themselves to get up, it is very easy to cause dislocation of the fracture site, wound tearing, and even secondary injury due to improper force, delaying the recovery cycle, and increasing the patient's pain and treatment costs.

[0003] For example, in Chinese patent publication number CN110897836A, an adaptive walker for orthopedic rehabilitation is provided. According to the patient's height, the walker and seat are raised or lowered to a suitable position by raising or lowering the pneumatic telescopic rod. Due to the sliding connection between the slider and the slide groove, the electric telescopic rod is extended and retracted to drive the fixed block and the rotating shaft to move horizontally, thereby moving the seat horizontally to a position convenient for the patient to sit and rest.

[0004] For example, in the Chinese patent publication number CN221770719U, an orthopedic rehabilitation walker is provided. Through the folding setting of the seat board, the patient can sit down and rest when the patient is physically exhausted or tired, without having to find an area with a seat or bench, which is convenient for the patient to use.

[0005] Although this type of walker can provide support when the patient needs to rest, it does not pay enough attention to the auxiliary function of the patient's getting up. It only provides handrails for the patient to use, and the patient still needs to rely on his or her own fragile limb muscles to complete the process of getting up. It cannot effectively share the strength required to get up, resulting in the patient's center of gravity being unbalanced when getting up, and there is a risk of falling. If the patient's force is applied to the wrong part, it will also cause secondary injuries to the patient. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem in the prior art that although it can provide support when the patient needs to rest, it does not pay enough attention to the auxiliary function of the patient's getting up. It only provides handrails for the patient to use for support. The patient still needs to rely on his or her own fragile limb muscles to complete the getting up process, and cannot effectively share the strength required for getting up, resulting in the patient's center of gravity being unbalanced when getting up, and there is a risk of falling. If the patient's force is applied to an inappropriate position, it will also cause secondary injuries to the patient.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] An orthopedic rehabilitation walker includes a frame, a cushion fixed to the top of the frame, an armrest fixed to the frame, upright posts fixed symmetrically to the frame, a support frame fixed between two upright posts, and further includes:

[0009] The standing mechanism is used to apply upward thrust to the patient when the patient stands up;

[0010] A flipping mechanism is used to apply an outward ejection force to the patient's buttocks when the patient stands up;

[0011] The standing mechanism and the turning mechanism are both installed on the supporting frame.

[0012] Preferably, the standing mechanism includes an electric push rod fixed to the bottom of the support frame, a lifting frame is fixed to the top of the electric push rod extension rod, a rotating rod 1 is rotated on the lifting frame through a bearing, and a support plate is fixed to the outer surface of the rotating rod 1.

[0013] Preferably, the standing mechanism further comprises a circular gear fixed at one end of the rotating rod, a rectangular rack is fixed at the top of the support frame, and the circular gear and the rectangular rack are meshed with each other.

[0014] Preferably, the flipping mechanism includes a second rotating rod fixed at the axis of the circular gear, a rotating drum is fixed on the outer surface of the second rotating rod, and a pull rope is fixed on the outer surface of the rotating drum.

[0015] Preferably, the flipping mechanism also includes a rectangular block fixed at the bottom of the support plate, a cross bar is fixed between the two rectangular blocks, a slider is slid on the outer surface of the cross bar, a reset spring is sleeved on the outer surface of the cross bar, the two ends of the reset spring are respectively fixedly connected to the rectangular block and the slider, and the end of the pull rope away from the rotating drum slides through the rectangular block and is fixedly connected to the slider.

[0016] Preferably, the support frame is also provided with an auxiliary mechanism for applying pressure to the patient's back, the auxiliary mechanism includes a connecting block fixed to one side of the slider, an extrusion rod is fixed on the connecting block, a mounting block is fixed to the bottom of the support plate, a liquid storage cylinder is fixed to a side of the mounting block close to the extrusion rod, and the extrusion rod slides in the liquid storage cylinder.

[0017] Preferably, a piston disc 1 is fixed to one end of the extrusion rod away from the connecting block, the piston disc 1 slides in the liquid storage cylinder, and the outer surface of the liquid storage cylinder is connected to a liquid outlet hose.

[0018] Preferably, the auxiliary mechanism further comprises a connecting rod fixed on the top of the lifting frame, a U-shaped plate is fixed on the top of the connecting rod, a cylinder is fixed on the back of the U-shaped plate, and the end of the liquid outlet hose away from the liquid storage cylinder is connected to the cylinder.

[0019] Preferably, the auxiliary mechanism also includes a piston disc 2 sliding in the cylinder, a forward rod is fixed to the side of the piston disc 2, the forward rod is slidably connected to the cylinder and the U-shaped plate, the outer surface of the forward rod is sleeved with a return spring 2, the two ends of the return spring 2 are respectively fixedly connected to the piston disc 2 and the cylinder, and a backrest plate is fixed to the end of the forward rod away from the piston disc 2.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Through the setting of the standing mechanism, when the patient needs to stand up, an upward thrust can be applied to the patient, making it easier for the patient to stand up. At the same time, the meshing structure of the circular gear and the rectangular rack can drive the support plate to flip outward during the rising process of the lifting frame, so that it can apply a catapult force to the patient's buttocks, further facilitating the patient to stand up. At the same time, through the meshing of the circular gear and the rectangular rack, it can also ensure that the two sets of electric push rods drive the lifting frame and both sides of the support plate to move upward synchronously, ensuring that the support plate maintains a stable angle during the rising process to avoid shaking. This design effectively shares the force required for the patient to stand up, reduces the risk of dislocation of the fracture or tearing of the wound due to improper force exerted by the patient, assists the patient to complete the standing up action safely and easily, improves the stability and safety of the standing up process, and makes up for the defect of the traditional walker in lacking lateral auxiliary force when standing up, helps the patient better adjust the center of gravity, prevents falling due to imbalance of the center of gravity during the standing up process, and further improves the safety and reliability of the standing up process.

[0022] 2. When the standing mechanism is working, the circular gear rotates to drive the rotating rod 2 and the rotating drum to rotate. The rotating drum reels the drawstring, pulling the slider to slide to the other side on the crossbar, so that the tension of the drawstring can exert downward pressure on the support plate, making the support plate easier to flip, reducing the pressure on the circular gear and the rectangular rack, and assisting the patient to complete the center of gravity transfer when standing up. At the same time, the reset spring 1 can automatically reset the slider after the action is completed, preparing for the next use.

[0023] 3. Through the setting of the auxiliary mechanism, while the flipping mechanism is running, it can also apply thrust to the patient's back, making the patient's getting up smoother, and once again assisting the patient to complete the getting up action safely and easily. At the same time, when not getting up, the backrest can assist the patient to maintain the correct sitting and standing posture, reduce the burden on the spine and back muscles, avoid strain or injury due to improper posture, and effectively protect the patient's back, thereby improving the comfort and safety of the patient during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a three-dimensional diagram of the overall structure of an orthopedic rehabilitation walker proposed by the present invention;

[0025] Figure 2 This is a schematic diagram of the overall structure of an orthopedic rehabilitation walker proposed by the present invention from another perspective;

[0026] Figure 3 This is a side view of the overall structure of an orthopedic rehabilitation walker proposed by the present invention;

[0027] Figure 4 An orthopedic rehabilitation walker proposed by the present invention Figure 3 A magnified view of the structure at center A;

[0028] Figure 5 This is a bottom view of the support plate structure of an orthopedic rehabilitation walker proposed by the present invention;

[0029] Figure 6 An orthopedic rehabilitation walker proposed by the present invention Figure 5 A magnified view of the structure at point B in the middle;

[0030] Figure 7 This is a rear view of the U-shaped plate structure of an orthopedic rehabilitation walker proposed by the present invention;

[0031] Figure 8 An orthopedic rehabilitation walker proposed by the present invention Figure 7 Enlarged view of the structure at point C in the middle.

[0032] In the figure: 1. frame; 11. cushion; 12. handrail; 2. column; 3. support frame; 41. electric push rod; 42. lifting frame; 43. rotating rod 1; 44. support plate; 45. circular gear; 46. rectangular rack; 51. rotating rod 2; 52. rotating drum; 53. pull rope; 54. rectangular block; 55. cross bar; 56. slider; 57. return spring 1; 61. connecting block; 62. extrusion rod; 63. mounting block; 64. liquid storage cylinder; 65. piston disc 1; 66. liquid outlet hose; 67. connecting rod; 68. U-shaped plate; 69. cylinder; 610. piston disc 2; 611. forward rod; 612. return spring 2; 613. backrest plate. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Example 1, refer to Figures 1-8An orthopedic rehabilitation walker includes a frame 1, a cushion 11 is fixed to the top of the frame 1, an armrest 12 is fixed to the frame 1, columns 2 are symmetrically fixed to the frame 1, a support frame 3 is fixed between the two columns 2, and further includes:

[0035] The standing mechanism is used to apply upward thrust to the patient when the patient stands up;

[0036] A flipping mechanism is used to apply an outward ejection force to the patient's buttocks when the patient stands up;

[0037] The standing mechanism and the turning mechanism are both installed on the supporting frame 3.

[0038] Furthermore, the standing mechanism includes an electric push rod 41 fixed to the bottom of the support frame 3, a lifting frame 42 is fixed to the top of the extension rod of the electric push rod 41, a rotating rod 43 is rotated on the lifting frame 42 through a bearing, and a support plate 44 is fixed to the outer surface of the rotating rod 43.

[0039] Furthermore, the standing mechanism also includes a circular gear 45 fixed to one end of the rotating rod 43, and a rectangular rack 46 is fixed to the top of the support frame 3, and the circular gear 45 and the rectangular rack 46 are engaged with each other.

[0040] When using the walker, the patient can hold the handrails 12 with both hands, so that the patient's upper limbs can be placed on the cushion 11 to provide support when the patient walks. Universal self-locking wheels and support legs are installed at the bottom of the frame 1. The universal self-locking wheels are used to facilitate the patient to move the walker after walking a certain distance. The support legs are used to support the frame 1 when not walking. When the patient needs to rest, the support frame 3 is fixedly installed on the column 2, which makes it convenient for the patient to sit down and rest. This is existing technology, so I will not go into details here.

[0041] Considering that the existing technology can provide support when the patient needs to rest, it pays insufficient attention to the auxiliary function of the patient's getting up. It only provides the handrail 12 for the patient to use, and the patient still needs to rely on his or her own fragile limb muscles to complete the process of getting up. It cannot effectively share the strength required for getting up, resulting in the patient's center of gravity being unbalanced when getting up, and there is a risk of falling. In addition, if the patient's force is applied in an improper position, it will also cause secondary injuries to the patient. The following improvements are now made:

[0042] When the patient needs to stand up from a sitting position, the electric push rod 41 fixed at the bottom of the support frame 3 is started, and the extension rod of the electric push rod 41 extends to drive the lifting frame 42 at the top to move vertically upward. During the rising process of the lifting frame 42, the rotating rod 43 on it rotates through the bearing and moves accordingly, and the support plate 44 fixed on the outer surface of the rotating rod 43 also rises synchronously, applying an initial upward thrust to the patient's buttocks.

[0043] At the same time, the circular gear 45 fixed at one end of the rotating rod 43 is meshed with the rectangular rack 46 fixed on the top of the support frame 3. As the lifting frame 42 rises, the circular gear 45 rotates under the constraint of the rectangular rack 46, driving the rotating rod 43 and the support plate 44 to flip outward, so that the support plate 44 generates an outward ejection force on the patient's buttocks while rising, helping the patient to get up more easily. In addition, the meshing structure of the circular gear 45 and the rectangular rack 46 ensures that the electric push rods 41 on both sides drive the lifting frame 42 and the support plate 44 to rise synchronously, maintaining a stable angle of the support plate 44 during the rising process to avoid shaking.

[0044] Further benefits of adopting the above method are: effectively sharing the force required for the patient to stand up, reducing the risk of fracture dislocation or wound tearing due to improper force, assisting the patient to complete the standing up action safely and easily, improving the stability and safety of the standing up process, and at the same time making up for the defect of traditional walkers in lacking lateral auxiliary force when standing up, helping patients to better adjust their center of gravity, and preventing falls due to imbalance of center of gravity during standing up, further improving the safety and reliability of the standing up process.

[0045] Example 2, refer to Figures 1-8 An orthopedic rehabilitation walker includes a frame 1, a cushion 11 is fixed to the top of the frame 1, an armrest 12 is fixed to the frame 1, columns 2 are symmetrically fixed to the frame 1, a support frame 3 is fixed between the two columns 2, and further includes:

[0046] The standing mechanism is used to apply upward thrust to the patient when the patient stands up;

[0047] A flipping mechanism is used to apply an outward ejection force to the patient's buttocks when the patient stands up;

[0048] The standing mechanism and the turning mechanism are both installed on the supporting frame 3.

[0049] Furthermore, the flipping mechanism includes a second rotating rod 51 fixed at the axis of the circular gear 45 , a rotating drum 52 is fixed to the outer surface of the second rotating rod 51 , and a pull rope 53 is fixed to the outer surface of the rotating drum 52 .

[0050] Furthermore, the flipping mechanism also includes a rectangular block 54 fixed at the bottom of the support plate 44, a cross bar 55 is fixed between the two rectangular blocks 54, a slider 56 is slid on the outer surface of the cross bar 55, and a return spring 57 is sleeved on the outer surface of the cross bar 55. The two ends of the return spring 57 are respectively fixedly connected to the rectangular block 54 and the slider 56, and the end of the pull rope 53 away from the rotating drum 52 slides through the rectangular block 54 and is fixedly connected to the slider 56.

[0051] It should be noted that: considering that only by rising the lifting frame 42, the circular gear 45 and the rectangular rack 46 cooperate to drive the rotating rod 1 43 and the support plate 44 to flip, generating an outward ejection force on the patient's buttocks, this will generate a large pressure on the circular gear 45 and the rectangular rack 46, which will have the risk of damage. The following improvements are now made:

[0052] The rotating drum 52 is connected to the circular gear 45. When the standing mechanism is running, the rotation of the circular gear 45 will drive the rotating rod 2 51 fixed at its axis to rotate synchronously, and the rotating drum 52 fixed on the outer surface of the rotating rod 2 51 will rotate accordingly. The pull rope 53 wrapped around the outer surface of the rotating drum 52 is wound, and the pull rope 53 pulls the slider 56 on the cross bar 55 to slide. The slider 56 overcomes the elastic force of the return spring 1 57 and moves to one side, so that the slider 56 slides to the bottom of the flip surface of the support plate 44.

[0053] A further benefit of adopting the above method is that when the slider 56 moves, the pull rope 53 applies a downward pulling force to the support plate 44, which makes the support plate 44 easier to flip outward, reducing the pressure on the circular gear 45 and the rectangular rack 46 during the flipping process. When the patient completes the standing up action, the electric push rod 41 contracts, the lifting frame 42 descends, the circular gear 45 rotates in the opposite direction, the pull rope 53 relaxes, and the reset spring 57 pushes the slider 56 to reset, preparing for the next use, and at the same time assisting the patient to complete the center of gravity transfer when standing up, preventing the imbalance of the center of gravity from causing a fall.

[0054] Example 3, refer to Figures 1-8 An orthopedic rehabilitation walker includes a frame 1, a cushion 11 is fixed to the top of the frame 1, an armrest 12 is fixed to the frame 1, columns 2 are symmetrically fixed to the frame 1, a support frame 3 is fixed between the two columns 2, and further includes:

[0055] The standing mechanism is used to apply upward thrust to the patient when the patient stands up;

[0056] A flipping mechanism is used to apply an outward ejection force to the patient's buttocks when the patient stands up;

[0057] The standing mechanism and the turning mechanism are both installed on the supporting frame 3.

[0058] Furthermore, the support frame 3 is also provided with an auxiliary mechanism for applying pressure to the patient's back, the auxiliary mechanism includes a connecting block 61 fixed to one side of the slider 56, an extrusion rod 62 is fixed on the connecting block 61, a mounting block 63 is fixed to the bottom of the support plate 44, and a liquid storage cylinder 64 is fixed to one side of the mounting block 63 close to the extrusion rod 62, and the extrusion rod 62 slides in the liquid storage cylinder 64.

[0059] Furthermore, a piston disc 65 is fixed to one end of the extrusion rod 62 away from the connecting block 61 , and the piston disc 65 slides in the liquid storage cylinder 64 , and the outer surface of the liquid storage cylinder 64 is connected to a liquid outlet hose 66 .

[0060] Furthermore, the auxiliary mechanism also includes a connecting rod 67 fixed to the top of the lifting frame 42, a U-shaped plate 68 is fixed to the top of the connecting rod 67, a cylinder 69 is fixed to the back of the U-shaped plate 68, and the end of the liquid outlet hose 66 away from the liquid storage cylinder 64 is connected to the cylinder 69.

[0061] Furthermore, the auxiliary mechanism also includes a piston disk 2 610 sliding in the cylinder 69, and a forward rod 611 is fixed to the side of the piston disk 2 610, and the forward rod 611 is slidably connected to the cylinder 69 and the U-shaped plate 68. The outer surface of the forward rod 611 is sleeved with a return spring 2 612, and the two ends of the return spring 2 612 are respectively fixedly connected to the piston disk 2 610 and the cylinder 69, and a backrest plate 613 is fixed to the end of the forward rod 611 away from the piston disk 2 610.

[0062] When the flip mechanism is running, the slider 56 slides and drives the connecting block 61 fixed on its side to move, and the extrusion rod 62 on the connecting block 61 moves accordingly. The extrusion rod 62 pushes the piston plate 65 to slide in the liquid storage cylinder 64, and presses the liquid in the liquid storage cylinder 64 into the cylinder body 69 through the liquid outlet hose 66.

[0063] After the liquid enters the cylinder 69, it pushes the piston disc 2 610, and the piston disc 2 610 drives the forward rod 611 to move. The forward rod 611 pushes the backrest board 613 to apply thrust to the patient's back, providing back support during the patient's getting up process, making the getting up movement smoother. When the patient has finished getting up, the electric push rod 41 contracts and the lifting frame 42 descends. Under the action of the reset spring 2 612, the piston disc 2 610, the forward rod 611 and the backrest board 613 are reset. In daily use, the backrest board 613 can also assist the patient to maintain correct sitting and standing postures, reduce the burden on the spine and back muscles, and protect the patient's back.

[0064] Through the mutual cooperation of the standing mechanism, the turning mechanism and the auxiliary mechanism, this orthopedic rehabilitation walker can achieve all-round assistance for the patient's standing up process, reduce the risk of secondary injury, and improve the safety and comfort of the patient during the rehabilitation process.

[0065] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An orthopedic rehabilitation walker, comprising a frame (1), characterized in that: A buffer pad (11) is fixed on the top of the frame (1), a handrail (12) is also fixed on the frame (1), upright posts (2) are symmetrically fixed on the frame (1), a support frame (3) is fixed between two upright posts (2), and further comprises: The standing mechanism is used to apply upward thrust to the patient when the patient stands up; A flipping mechanism is used to apply an outward ejection force to the patient's buttocks when the patient stands up; The standing mechanism and the turning mechanism are both installed on the supporting frame (3).

2. The orthopedic rehabilitation walker according to claim 1, characterized in that: The standing mechanism comprises an electric push rod (41) fixed at the bottom of the support frame (3), a lifting frame (42) is fixed to the top end of the extension rod of the electric push rod (41), a rotating rod (43) is rotated on the lifting frame (42) through a bearing, and a support plate (44) is fixed to the outer surface of the rotating rod (43).

3. The orthopedic rehabilitation walker according to claim 2, characterized in that: The standing mechanism further comprises a circular gear (45) fixed to one end of a rotating rod (43), a rectangular rack (46) is fixed to the top of the support frame (3), and the circular gear (45) and the rectangular rack (46) are meshed with each other.

4. The orthopedic rehabilitation walker according to claim 3, characterized in that: The turning mechanism comprises a second rotating rod (51) fixed at the axis of the circular gear (45), a rotating drum (52) is fixed on the outer surface of the second rotating rod (51), and a pulling rope (53) is fixed on the outer surface of the rotating drum (52).

5. The orthopedic rehabilitation walker according to claim 4, characterized in that: The flipping mechanism also includes a rectangular block (54) fixed at the bottom of the support plate (44), a cross bar (55) is fixed between the two rectangular blocks (54), a slider (56) is slid on the outer surface of the cross bar (55), a return spring (57) is sleeved on the outer surface of the cross bar (55), and the two ends of the return spring (57) are respectively fixedly connected to the rectangular block (54) and the slider (56), and the end of the pull rope (53) away from the rotating drum (52) slides through the rectangular block (54) and is fixedly connected to the slider (56).

6. The orthopedic rehabilitation walker according to claim 5, characterized in that: The support frame (3) is also provided with an auxiliary mechanism for applying pressure to the patient's back, the auxiliary mechanism comprising a connecting block (61) fixed to one side of the slider (56), an extrusion rod (62) fixed to the connecting block (61), a mounting block (63) fixed to the bottom of the support plate (44), a liquid storage cylinder (64) fixed to one side of the mounting block (63) close to the extrusion rod (62), and the extrusion rod (62) slides in the liquid storage cylinder (64).

7. The orthopedic rehabilitation walker according to claim 6, characterized in that: A piston disc 1 (65) is fixed to one end of the extrusion rod (62) away from the connecting block (61), and the piston disc 1 (65) slides in the liquid storage cylinder (64). The outer surface of the liquid storage cylinder (64) is connected to a liquid outlet hose (66).

8. The orthopedic rehabilitation walker according to claim 7, characterized in that: The auxiliary mechanism further comprises a connecting rod (67) fixed on the top of the lifting frame (42), a U-shaped plate (68) is fixed on the top of the connecting rod (67), a cylinder (69) is fixed on the back of the U-shaped plate (68), and the end of the liquid outlet hose (66) away from the liquid storage cylinder (64) is connected to the cylinder (69).

9. The orthopedic rehabilitation walker according to claim 8, characterized in that: The auxiliary mechanism also includes a second piston disc (610) sliding in the cylinder (69), a forward rod (611) is fixed to the side of the second piston disc (610), the forward rod (611) is slidably connected to the cylinder (69) and the U-shaped plate (68), the outer surface of the forward rod (611) is sleeved with a second return spring (612), the two ends of the second return spring (612) are respectively fixedly connected to the second piston disc (610) and the cylinder (69), and a backrest plate (613) is fixed to the end of the forward rod (611) away from the second piston disc (610).

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