Seat backrest adjusting structure

Abstract

The utility model relates to the technical field of seats, in particular to a seat backrest adjusting structure which comprises a backrest and a seat, a backrest fixing seat is arranged on the back portion of the backrest, a seat supporting seat is arranged at the bottom of the seat, a positioning piece of a U-shaped structure is arranged in the seat supporting seat, an air cylinder is installed in the positioning piece, and the air cylinder is connected with the air cylinder. A first air cylinder connecting rod and a second air cylinder connecting rod are inserted into the two ends of the air cylinder correspondingly, a limiting seat is clamped and fixed to the inner side of the backrest fixing seat, side plates are symmetrically connected to the two sides of the limiting seat and clamped in a positioning piece, and arc-shaped connecting rods are symmetrically arranged on the outer side of the end, close to the limiting seat, of the positioning piece; and a limiting connecting piece is clamped between the arc-shaped connecting rods. According to the seat backrest adjusting structure, angle adjustment and front-and-back adjustment of the backrest can be conducted after the seat is subjected to the gravity effect, manual adjustment is reduced, meanwhile, the backrest can be tightly attached to the back of a user all the time through supporting of the pneumatic cylinder, and the better supporting effect is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a seat backrest adjusting structure. BACKGROUND

[0002] The seat is designed for children and teenagers, can adjust the backrest position, prevent incorrect sitting posture from causing bad posture, distraction and long-term health problems, and can prevent spinal problems and improve learning efficiency.

[0003] The existing seat realizes the rotatable treatment of the backrest through manual lever, knob, pneumatic cylinder and other structures, but the backrest is inconvenient for automatic rotation and forward and backward movement, and needs manual adjustment. UTILITY MODEL CONTENTS

[0004] The utility model discloses a seat backrest adjusting structure to solve the problem that the backrest of the seat on the market is inconvenient for automatic rotation and forward and backward movement and needs manual adjustment.

[0005] To achieve the above object, the utility model provides the following technical scheme: a seat backrest adjusting structure, including backrest and seat, the backrest back is equipped with backrest fixed seat, the seat bottom is equipped with seat support seat, the seat support seat is equipped with the positioning piece of U type structure in, and the positioning piece is installed the cylinder, and the both ends of cylinder are inserted with first cylinder connecting rod and second cylinder connecting rod respectively, the inboard of backrest fixed seat is connected fixedly with the limit seat, and the both sides of limit seat are connected with the side plate symmetrically, and the side plate is clamped in the positioning piece, the outside of the one end of positioning piece close to limit seat is equipped with the arc connecting rod symmetrically, and the arc connecting rod is still clamped with the limit connecting piece between, the both sides of the middle position of positioning piece are equipped with the connecting rod symmetrically, and the upper of positioning piece is equipped with the fixed part that is connected with seat, the inboard of backrest fixed seat still is equipped with the linkage rod, and the upper and lower of linkage rod are equipped with upper connecting hole and lower connecting hole respectively.

[0006] Preferably, the seat support seat is integrally provided with a support rod positioning seat, a supporting plate and a round hole table, and the supporting plate is supported below the limit seat.

[0007] Preferably, the positioning member is symmetrically provided with a second cylinder connecting rod fixing hole on both sides for penetrating and cooperating with the second cylinder connecting rod, and the front end of the positioning member is further provided with a limiting clamping groove for clamping and cooperating with the support rod positioning seat, the end of the positioning member close to the limiting seat is symmetrically provided with an arc-shaped backrest angle adjusting limiting hole on both sides, and the first cylinder connecting rod is inserted into the backrest angle adjusting limiting hole, the first linkage fixing hole and the second linkage fixing hole are symmetrically provided on both sides of the positioning member above the backrest angle adjusting limiting hole, the bottom of the positioning member is further provided with a fastening hole corresponding to the round hole table position, and the connecting rod fixing hole corresponding to the connecting rod position is further provided on both sides of the positioning member.

[0008] Preferably, the connecting rod is respectively provided with a first movable connecting hole and a second movable connecting hole at both ends, the first movable connecting hole corresponds to the position of the connecting rod fixing hole, and the second movable connecting hole is located in front of the fixing member.

[0009] Preferably, the limiting connecting member is a U-shaped structure, and the limiting connecting member is provided with a limiting groove corresponding to the position of the cylinder above, and the front connecting hole and the rear connecting hole are further respectively provided on both sides of the limiting connecting member, and the rear connecting hole corresponds to the position of the second linkage fixing hole.

[0010] Preferably, the limiting seat is uniformly and spacedly provided with a backrest fixing seat connecting hole for bolt connection with the backrest fixing seat on the back, and the limiting seat is provided with a groove for clamping the linkage rod above, the side plate is an L-shaped plate structure, and the first positioning connecting hole is provided on the upper part of the rear of the side plate, and the limiting seat upper connecting hole and the limiting seat lower connecting hole are respectively provided on the upper end and the lower end of the front of the side plate, the limiting seat upper connecting hole corresponds to the position of the first linkage fixing hole, and the limiting seat lower connecting hole corresponds to the position of the backrest angle adjusting limiting hole.

[0011] Preferably, the arc-shaped connecting rod is provided with an arc-shaped connecting rod upper fixing hole, an arc-shaped connecting rod middle fixing hole and an arc-shaped connecting rod lower fixing hole at the upper, middle and lower parts, respectively, the arc-shaped connecting rod upper fixing hole corresponds to the position of the first positioning connecting hole, the arc-shaped connecting rod middle fixing hole corresponds to the position of the limiting seat upper connecting hole, and the arc-shaped connecting rod lower fixing hole corresponds to the position of the front connecting hole.

[0012] Compared with the prior art, the seat backrest adjusting structure can adjust the angle and the front and back of the seat backrest after being subjected to the action of gravity, reduce manual adjustment, and the backrest can always be close to the back of the user through the support of the pneumatic cylinder, thereby playing a better supporting role. The seat backrest adjusting structure can connect the backrest fixing seat and the seat support seat through the pneumatic cylinder, realize linkage adjustment between the backrest fixing seat and the seat support seat, and ensure the use performance of the seat. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 It is external structure schematic view of the seat backrest adjusting structure of the utility model;

[0014] Figure 2 It is side view of the seat backrest adjusting structure of the utility model;

[0015] Figure 3 It is seat support seat and backrest fixed seat connecting structure schematic view of the seat backrest adjusting structure of the utility model;

[0016] Figure 4 It is the connecting structure overhead view of the positioning piece and the seat support seat of the seat backrest adjusting structure of the utility model;

[0017] Figure 5 It is the connecting structure three-dimensional structure schematic view of the positioning piece and the seat support seat of the seat backrest adjusting structure of the utility model;

[0018] Figure 6 It is the connecting structure schematic view of the positioning piece and the limiting seat of the seat backrest adjusting structure of the utility model;

[0019] Figure 7 It is external structure schematic view of the seat support seat of the seat backrest adjusting structure of the utility model;

[0020] Figure 8 It is internal structure schematic view of the seat support seat of the seat backrest adjusting structure of the utility model;

[0021] Figure 9 It is the linkage rod structure schematic view of the seat backrest adjusting structure of the utility model;

[0022] Figure 10 It is the fixed piece structure schematic view of the seat backrest adjusting structure of the utility model;

[0023] Figure 11 It is the positioning piece structure schematic view of the seat backrest adjusting structure of the utility model;

[0024] Figure 12 It is the limiting connecting piece structure schematic view of the seat backrest adjusting structure of the utility model;

[0025] Figure 13 It is the limiting seat structure schematic view of the seat backrest adjusting structure of the utility model;

[0026] Figure 14 It is the arc-shaped connecting rod structure schematic view of the seat backrest adjusting structure of the utility model.

[0027] In the figure: 1, backrest; 2, seat; 3, backrest fixing seat; 4, seat support seat; 401, support rod positioning seat; 402, support plate; 403, round hole table; 5, linkage rod; 501, upper connecting hole; 502, lower connecting hole; 6, fixing piece; 7, positioning piece; 701, backrest angle adjustment limiting hole; 702, fastening hole; 703, limiting clamping groove; 704, connecting rod fixing hole; 705, second air cylinder connecting rod fixing hole; 706, first linkage fixing hole; 707, second linkage fixing hole; 8, connecting rod; 801, first movable connecting hole; 802, second movable connecting hole; 9, limiting connecting piece; 901, limiting groove; 902, front connecting hole; 903, rear connecting hole; 10, limiting seat; 1001, side plate; 1002, backrest fixing seat connecting hole; 1003, first positioning connecting hole; 1004, limiting seat upper connecting hole; 1005, limiting seat lower connecting hole; 11, arc-shaped connecting rod; 1101, upper part of arc-shaped connecting rod fixed hole; 1102, middle part of arc-shaped connecting rod fixed hole; 1103, lower part of arc-shaped connecting rod fixed hole; 12, air cylinder; 1201, first air cylinder connecting rod; 1202, second air cylinder connecting rod. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] Please refer to Figures 1-14The utility model provides a technical scheme: a seat backrest adjusting structure, including backrest 1 and seat 2, backrest 1 back is equipped with backrest fixed seat 3, seat 2 bottom is equipped with seat support seat 4, the inside of seat support seat 4 is equipped with the positioning piece 7 of U type structure, the integral seat support seat 4 is equipped with support rod positioning seat 401, support plate 402 and round hole platform 403, and support plate 402 supports in the below of limit seat 10, this structure can pass through the fixing treatment of support rod positioning seat 401 that seat support seat 4 sets up and carry out seat 2 base support frame fixing, support plate 402 can play the role of supporting to limit seat 10, ensure that backrest fixed seat 3 is opposite seat support seat 4 position stable, and positioning piece 7 installs cylinder 12 in, and cylinder 12 both ends are inserted respectively first cylinder connecting rod 1201 and second cylinder connecting rod 1202, backrest fixed seat 3 inner side joint fixed limit seat 10, and limit seat 10 both sides are connected with side plate 1001 symmetrically, and side plate 1001 is clamped in positioning piece 7, positioning piece 7 is close to the outside symmetry of limit seat 10 one end and is equipped with arc connecting rod 11, and arc connecting rod 11 between still clamping limit connecting piece 9, positioning piece 7 both sides of middle part are equipped with connecting rod 8 symmetrically, positioning piece 7 both sides are equipped with second cylinder connecting rod fixed hole 705 that second cylinder connecting rod 1202 penetrates and cooperates symmetrically, and positioning piece 7 front end still is equipped with with support rod positioning seat 401 clamping cooperation's limit clamping groove 703, positioning piece 7 is close to the arc structure's backrest angle adjustment limit hole 701 that limit seat 10 one end both sides open symmetrically, and first cylinder connecting rod 1201 is inserted in backrest angle adjustment limit hole 701, positioning piece 7 both sides are equipped with first linkage fixed hole 706 and second linkage fixed hole 707 above backrest angle adjustment limit hole 701, positioning piece 7 bottom still is equipped with with round hole platform 403 position corresponding fastening hole 702, and positioning piece 7 both sides still are equipped with with connecting rod 8 position corresponding connecting rod fixed hole 704, this structure makes connecting rod 8 to fixed piece 6 and positioning piece 7 play the role of relative connection, simultaneously, connecting rod 8 is connected to fixed piece 6 and limit connecting piece 9 and handles, ensure that fixed piece 6 supports positioning of seat 2, and when seat 2 is subjected to gravity, fixed piece 6 can drive connecting rod 8 and limit connecting piece 9 to rotate, thereby through limit connecting piece 9 drive side plate 1001 to rotate, further realize the angle adjustment of backrest fixed seat 3, linkage rod 5 play the role of movable limit to the position below backrest fixed seat 3, simultaneously, the activity of backrest fixed seat 3 will be through linkage rod 5 and act to backrest 1, backrest 1 is through the rotary connection of with upper connecting hole 501, can realize rotary handling, make backrest 1 close to the back of user, cylinder 12 is positioned in positioning piece 7 through second cylinder connecting rod fixed hole 705 and backrest angle adjustment limit hole 701, can make backrest 1 after being subjected to thrust, backrest fixed seat 3 is driven cylinder 12 to carry out telescopic adjustment through linkage rod 5, realize the fore-and-aft adjustment of backrest fixed seat 3,The first movable connecting hole 801 and the second movable connecting hole 802 are arranged at two ends of the connecting rod 8 respectively, the first movable connecting hole 801 corresponds to the position of the connecting rod fixing hole 704, and the second movable connecting hole 802 is located on the front side of the fixing part 6, the connecting rod 8 is located on the outer side of the fixing part 6, the structure of the connecting rod 8 can realize relative connection of the fixing part 6, the positioning part 7 and the limiting connecting part 9, and ensure that the seat 2 can move after being subjected to gravity, the limiting connecting part 9 is in a U-shaped structure, a limiting groove 901 corresponding to the position of the air cylinder 12 is arranged on the upper side of the limiting connecting part 9, front and rear connecting holes 902 and 903 are arranged on the front and rear sides of the limiting connecting part 9 respectively, the rear connecting hole 903 corresponds to the position of the second linkage fixing hole 707, the structure can avoid affecting the air cylinder 12 through the limiting groove 901 when the limiting connecting part 9 moves, the limiting connecting part 9 can realize relative connection of the positioning part 7 and the side plate 1001, the second air cylinder connecting rod fixing hole 705 and the arc-shaped connecting rod middle fixing hole 1102 can position the air cylinder 12, the backrest angle adjusting limiting hole 701 can limit the first air cylinder connecting rod 1201, the fixing part 6 is arranged on the upper side of the positioning part 7 and connected with the seat 2, the back of the limiting seat 10 is uniformly and spacedly provided with backrest fixing seat connecting holes 1002 which are bolted with the backrest fixing seat 3, grooves are arranged on the upper side of the limiting seat 10 and engaged with the linkage rod 5, the side plate 1001 is in an L-shaped plate structure, a first positioning connecting hole 1003 is arranged on the upper side of the rear side of the side plate 1001, limiting seat upper and lower connecting holes 1004 and 1005 are arranged on the upper and lower ends of the front side of the side plate 1001 respectively, the limiting seat upper connecting hole 1004 corresponds to the position of the first linkage fixing hole 706, and the limiting seat lower connecting hole 1005 corresponds to the position of the backrest angle adjusting limiting hole 701, the structure can limit the linkage rod 5 through the limiting seat 10 when the linkage rod 5 moves, the side plate 1001 can move relative to the backrest angle adjusting limiting hole 701 under the positioning of the first linkage fixing hole 706 by being connected with the positioning part 7, the angle of the side plate 1001 can be adjusted, the backrest fixing seat 3 can move forward and backward and the angle can be adjusted, the linkage rod 5 is further arranged on the inner side of the backrest fixing seat 3, upper and lower connecting holes 501 and 502 are arranged on the upper and lower sides of the linkage rod 5 respectively, the upper connecting hole 501 is penetrated and connected with the backrest fixing seat 3 and the backrest 1, the lower connecting hole 502 is penetrated and connected with the first air cylinder connecting rod 1201, arc-shaped connecting rod upper, middle and lower fixing holes 1101, 1102 and 1103 are arranged on the upper, middle and lower sides of the arc-shaped connecting rod 11 respectively, the arc-shaped connecting rod upper fixing hole 1101 corresponds to the position of the first positioning connecting hole 1003, the arc-shaped connecting rod middle fixing hole 1102 corresponds to the position of the limiting seat upper connecting hole 1004, and the arc-shaped connecting rod lower fixing hole 1103 corresponds to the position of the front connecting hole 902.This structure plays a role of relative connection to the side plate 1001, the limiting connecting piece 9 and the positioning piece 7 through the arc-shaped connecting rod 11, and realizes reliable connection of the limiting connecting piece 9 and the side plate 1001 relative to the positioning piece 7.

[0030] Working principle: when using the seat backrest adjusting structure, first, the seat support seat 4 supports the seat 2 from the bottom, and the supporting plate 402 supports the lower part of the backrest fixing seat 3, the support rod positioning seat 401 is used for fixing the bottom support frame, when the user sits on the seat 2, the fixed part 6 drives the connecting rod 8 and the limiting connecting part 9 to move under the action of gravity, the first movable connecting hole 801 is used for movably connecting the connecting rod 8 and the fixed part 6, the front connecting hole 902 is used for movably connecting the limiting connecting part 9 and the fixed part 6, the connecting rod 8 is fixed relative to the positioning part 7 through the cooperation of the second movable connecting hole 802 and the connecting rod fixing hole 704, the positioning part 7 is fastened in the seat support seat 4 through the cooperation of the fastening hole 702 and the circular hole table 403, the limiting slot 703 is used for limiting the positioning part 7 and the support rod positioning seat 401, after the limiting connecting part 9 rotates, the arc-shaped connecting rod 11 is driven to rotate through the cooperation of the front connecting hole 902 and the arc-shaped connecting rod lower fixing hole 1103, so that the arc-shaped connecting rod 11 rotates relative to the positioning part 7 under the positioning of the arc-shaped connecting rod middle fixing hole 1102, at this time, the arc-shaped connecting rod 11 drives the side plate 1001 to move through the arc-shaped connecting rod upper fixing hole 1101, so that the limiting seat 10 drives the backrest fixing seat 3 to adjust the angle, so that the backrest 1 can be placed on the back of the user, the backrest 1 can rotate relative to the linkage rod 5 through the upper connecting hole 501, so as to realize the self-adaptive adjustment of the angle of the backrest 1, after the backrest fixing seat 3 moves, the linkage rod 5 drives the first cylinder connecting rod 1201 to move through the lower connecting hole 502, so as to realize the telescopic adjustment of the cylinder 12, since the backrest angle adjusting limiting hole 701 limits the movement of the first cylinder connecting rod 1201, the front and back movement of the backrest fixing seat 3 can be realized, so as to ensure that the backrest 1 always fits the back of the user, the second cylinder connecting rod 1202 drives the cylinder 12 to rotate relative to the positioning part 7 through the second cylinder connecting rod fixing hole 705, the positioning part 7 is connected through the first linkage fixing hole 706, the arc-shaped connecting rod middle fixing hole 1102 and the limiting seat upper connecting hole 1004, so as to realize the connection of the arc-shaped connecting rod 11 relative to the positioning part 7 and the side plate 1001, the rear connecting hole 903 is connected relative to the positioning part 7 through the second linkage fixing hole 707, so as to realize the rotary positioning of the positioning part 7 relative to the limiting connecting part 9, when the limiting connecting part 9 moves, the limiting slot 901 avoids hindering the cylinder 12, the backrest fixing seat connecting hole 1002 is used for connecting the limiting seat 10 and the backrest fixing seat 3, the first positioning connecting hole 1003 is used for connecting the arc-shaped connecting rod 11 and the side plate 1001 through the cooperation of the arc-shaped connecting rod upper fixing hole 1101, so that the side plate 1001 can rotate relative to the positioning part 7 through the arc-shaped connecting rod 11, the limiting seat lower connecting hole 1005 corresponds to the position of the backrest angle adjusting limiting hole 701, so as to realize the rotation and the limiting movement of the side plate 1001 relative to the positioning part 7, so as to complete a series of work.

[0031] Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent replacement to part of the technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A seat back adjusting structure comprising a seat back (1) and a seat (2), the seat back (1) being provided with a seat back fixing seat (3) at the back thereof, and the seat (2) being provided with a seat support seat (4) at the bottom thereof, characterized in that: The seat support seat (4) is provided with a U-shaped positioning member (7), a gas cylinder (12) is installed in the positioning member (7), and first and second gas cylinder connecting rods (1201) and (1202) are respectively inserted into the two ends of the gas cylinder (12), the inner side of the backrest fixing seat (3) is clamped and fixed with a limiting seat (10), the two sides of the limiting seat (10) are symmetrically connected with side plates (1001), the side plates (1001) are clamped in the positioning member (7), the outer side of one end of the positioning member (7) close to the limiting seat (10) is symmetrically provided with arc-shaped connecting rods (11), and the arc-shaped connecting rods (11) are further clamped with a limiting connecting member (9), the two sides of the middle part of the positioning member (7) are symmetrically provided with connecting rods (8), and the upper side of the positioning member (7) is provided with a fixing member (6) connected with the seat (2), and the inner side of the backrest fixing seat (3) is further provided with a linkage rod (5), and the upper and lower sides of the linkage rod (5) are respectively provided with upper and lower connecting holes (501) and (502).

2. The seat back adjustment structure according to claim 1, characterized by: The seat support seat (4) is provided with a U-shaped positioning member (7), a gas cylinder (12) is installed in the positioning member (7), and first and second gas cylinder connecting rods (1201) and (1202) are respectively inserted into the two ends of the gas cylinder (12), the inner side of the backrest fixing seat (3) is clamped and fixed with a limiting seat (10), the two sides of the limiting seat (10) are symmetrically connected with side plates (1001), the side plates (1001) are clamped in the positioning member (7), the outer side of one end of the positioning member (7) close to the limiting seat (10) is symmetrically provided with arc-shaped connecting rods (11), and the arc-shaped connecting rods (11) are further clamped with a limiting connecting member (9), the two sides of the middle part of the positioning member (7) are symmetrically provided with connecting rods (8), and the upper side of the positioning member (7) is provided with a fixing member (6) connected with the seat (2), and the inner side of the backrest fixing seat (3) is further provided with a linkage rod (5), and the upper and lower sides of the linkage rod (5) are respectively provided with upper and lower connecting holes (501) and (502).

3. The seat back adjustment structure according to claim 2, characterized by: The two sides of the positioning member (7) are symmetrically provided with second gas cylinder connecting rod fixing holes (705) through which the second gas cylinder connecting rods (1202) pass, the front end of the positioning member (7) is further provided with limiting clamping grooves (703) clamped with the support rod positioning seat (401), the two sides of one end of the positioning member (7) close to the limiting seat (10) are symmetrically provided with backrest angle adjusting limiting holes (701) of arc-shaped structure, the first gas cylinder connecting rods (1201) are inserted into the backrest angle adjusting limiting holes (701), the two sides of the positioning member (7) are symmetrically provided with first and second linkage fixing holes (706) and (707) above the backrest angle adjusting limiting holes (701), the bottom of the positioning member (7) is further provided with fastening holes (702) corresponding to the positions of the round hole tables (403), and the two sides of the positioning member (7) are further provided with connecting rod fixing holes (704) corresponding to the positions of the connecting rods (8).

4. The seat back adjustment structure according to claim 3, characterized by: The two ends of the connecting rod (8) are respectively provided with first and second movable connecting holes (801) and (802), the first movable connecting hole (801) corresponds to the position of the connecting rod fixing hole (704), and the second movable connecting hole (802) is located in front of the fixing member (6), and the connecting rod (8) is located on the outer side of the fixing member (6).

5. The seat back adjustment structure according to claim 4, characterized by: The limiting connecting member (9) is of U-shaped structure, the upper side of the limiting connecting member (9) is provided with a limiting groove (901) corresponding to the position of the gas cylinder (12), the front and rear sides of the two sides of the limiting connecting member (9) are further provided with front and rear connecting holes (902) and (903), and the rear connecting hole (903) corresponds to the position of the second linkage fixing hole (707).

6. The seat back adjustment structure according to claim 5, characterized by: The back of the limiting seat (10) is uniformly spaced apart and provided with a backrest fixing seat connecting hole (1002) which is bolted with the backrest fixing seat (3), and the upper part of the limiting seat (10) is provided with a groove which is engaged with the linkage rod (5), the side plate (1001) is an L-shaped plate structure, and the upper part of the rear of the side plate (1001) is provided with a first positioning connecting hole (1003), and the upper and lower ends of the front of the side plate (1001) are respectively provided with a limiting seat upper connecting hole (1004) and a limiting seat lower connecting hole (1005), the limiting seat upper connecting hole (1004) corresponds to the position of the first linkage fixing hole (706), and the limiting seat lower connecting hole (1005) corresponds to the position of the backrest angle adjusting limiting hole (701).

7. The seat back adjustment structure according to claim 6, characterized by: The upper, middle and lower parts of the arc-shaped connecting rod (11) are respectively provided with an arc-shaped connecting rod upper fixing hole (1101), an arc-shaped connecting rod middle fixing hole (1102) and an arc-shaped connecting rod lower fixing hole (1103), the arc-shaped connecting rod upper fixing hole (1101) corresponds to the position of the first positioning connecting hole (1003), the arc-shaped connecting rod middle fixing hole (1102) corresponds to the position of the limiting seat upper connecting hole (1004), and the arc-shaped connecting rod lower fixing hole (1103) corresponds to the position of the front connecting hole (902).

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