Hydraulic tunnel excavation support structure

Abstract

The utility model discloses a water conservancy tunnel excavation support structure relates to tunnel support technical field, it includes steel arch, still includes: two bases, all are seted up adjusting groove on the upside, and the adjusting groove opposite two groove walls all are seted up two guide holes, and the two guide holes on same groove wall all are inclined extension and from below and above each other away, four adjusting bars, two two settings are in two adjusting grooves, and the both ends of each adjusting bar are respectively adapted and slide connection in the opposite two guide holes, two support frames, the lower end is respectively adapted and slide connection in two adjusting grooves, and the upper end is respectively fixedly connected in the both ends of steel arch, and the downside all abuts on corresponding two adjusting bars, two groups of linear drive assembly, two groups of linear drive assembly are respectively installed in two bases, and the drive end of two groups of linear drive assembly simultaneously transmission connection in corresponding two adjusting bars. The present application can improve the technical problem of inconveniently adjusting the support height of the both ends of steel arch in the prior art.

Description

Technical Field

[0001] This application relates to the field of tunnel support technology, and in particular to a hydraulic tunnel excavation support structure. Background Technology

[0002] Tunnel excavation and support is a crucial step in tunnel construction. Construction workers pre-support the surrounding rock to enhance its stability and resistance to deformation, thereby ensuring the safety, stability, and smooth progress of tunnel construction. During tunnel excavation, steel arch supports are commonly used to ensure tunnel stability and construction safety.

[0003] In existing technologies, when installing steel arch frames, column base platforms or concrete piers are typically installed in the tunnel to provide support for the lower end of the steel arch frame. However, this support method cannot adjust the support height at both ends of the steel arch frame, and cannot guarantee that both ends of the steel arch frame are at the same support height. Utility Model Content

[0004] This application provides a hydraulic tunnel excavation support structure to improve the technical problem in the prior art that it is inconvenient to adjust the support height at both ends of the steel arch frame and cannot ensure that both ends of the steel arch frame are at the same support height.

[0005] This application provides a hydraulic tunnel excavation support structure, which adopts the following technical solution:

[0006] A hydraulic tunnel excavation support structure includes a steel arch frame, and further includes:

[0007] Two bases, each with an adjustment groove on its upper side, and two guide holes on the two opposite walls of the adjustment grooves. The two guide holes on the same wall extend obliquely and move away from each other from bottom to top.

[0008] Four adjusting rods are arranged in pairs in the two adjusting slots, and the two ends of each adjusting rod are respectively adapted to and slidably connected to the two opposite guide holes;

[0009] Two support frames, the lower ends of the two support frames are respectively adapted to and slidably connected to the two adjustment slots, the upper ends are respectively fixedly connected to the two ends of the steel arch frame, and the lower sides of the two support frames abut against the corresponding two adjustment rods;

[0010] Two linear drive assemblies are respectively mounted on two bases, and the drive ends of the two linear drive assemblies are simultaneously connected to the corresponding two adjusting rods.

[0011] Optionally, the two opposite walls of the adjusting groove are provided with clearance holes located between the two corresponding guide holes; both sets of linear drive assemblies include gears, racks, and two first telescopic rods. Each first telescopic rod includes a sleeve and two rod cores. The two ends of the sleeve are provided with internal threads in opposite directions. One end of each of the two rod cores is threaded to both ends of the sleeve, and the other end of each rod core is fixedly connected to the corresponding adjusting rod. The gears are coaxially fixedly connected to the sleeves, and the rack meshes with both gears simultaneously, with its two ends extending from the two clearance holes respectively.

[0012] Optionally, each of the rod sleeves has an annular groove coaxially formed on its side wall, and each of the first telescopic rods also includes a limiting rod that is vertically slidably connected to the base.

[0013] Optionally, the rack has a straight groove on its side wall, and each of the limiting rods is fixedly connected to a connecting rod, with the end of each connecting rod adapted to and slidably connected to the straight groove.

[0014] Optionally, each of the four adjusting rods includes an adjusting shaft and two adjusting seats rotatably connected to both ends of the adjusting shaft. The rod portion of each adjusting shaft abuts against the lower side of the support frame and is drivenly connected to the drive end of the corresponding linear drive assembly. Each adjusting seat is adapted to and slidably connected to the corresponding guide hole.

[0015] Optionally, each of the four adjusting rods further includes multiple adjusting rings, each adjusting ring being spaced apart from the corresponding adjusting shaft and coaxially rotatably connected to the corresponding adjusting shaft, the adjusting shaft abutting against the lower side of the support frame through each adjusting ring.

[0016] Optionally, the side wall of the base is provided with four oblique holes, which are connected to each of the guide holes, and the four oblique holes are inclined in a direction parallel to the corresponding guide holes; each of the four adjusting rods also includes two hanging rods and multiple nuts, one end of each hanging rod is fixedly connected to the corresponding adjusting seat, and each nut is threadedly connected to the other end of each hanging rod and abuts against the base.

[0017] Optionally, both support frames include a support base that is adapted and slidably connected to a corresponding support base, a support ball rotatably connected to the upper end of the support base, a support rod whose lower end is fixedly connected to the support ball, and a support plate whose lower end is fixedly connected to the upper end of the support rod. The two ends of the steel arch frame are respectively fixedly connected to the upper ends of the two support plates. Both support frames also include a second telescopic rod. The second telescopic rod is vertically arranged and its two ends are respectively rotatably connected to the corresponding support base and the support plate. The vertical plane formed by the axis of the second telescopic rod and the center of the corresponding support ball is perpendicular to the plane where the steel arch frame is located.

[0018] Optionally, each of the two second telescopic rods includes a rod cylinder rotatably connected to the support base at its lower end, a screw threadedly connected to the rod cylinder at its lower end, and an adapter rotatably connected to the upper end of the screw at its lower end, the upper end of the adapter being rotatably connected to the support plate.

[0019] Optionally, each of the two second telescopic rods further includes four ear plates that are fixedly connected in pairs to the corresponding support base and the support plate. The lower end of the rod tube is fixedly connected to a first adapter shaft whose two ends are rotatably connected to the two corresponding ear plates. The upper end of the adapter is rotatably connected to a second adapter shaft whose two ends are rotatably connected to the two corresponding ear plates.

[0020] In summary, this application includes the following beneficial technical effects:

[0021] When installing the steel arch frame, the two corresponding adjusting rods can be moved simultaneously by the linear drive assembly located at the lower end of the steel arch frame. This allows the two adjusting rods to move obliquely upwards under the guidance of the corresponding guide holes, thereby pushing the corresponding support frame upwards. This adjusts the support height of the corresponding support frame at the end of the steel arch frame, improving the technical problem in the prior art where it is inconvenient to adjust the support height at both ends of the steel arch frame and cannot ensure that both ends of the steel arch frame are at the same support height. Attached Figure Description

[0022] Figure 1 This is a structural diagram of the present invention.

[0023] Figure 2 This is a first partial structural cross-sectional view of the present invention.

[0024] Figure 3 yes Figure 2 Enlarged view of part A in the middle.

[0025] Figure 4 yes Figure 2 Enlarged view of section B in the middle.

[0026] Figure 5This is a second partial structural cross-sectional view of the present invention, in which the second telescopic rod is shown as an exploded structure.

[0027] Figure 6 yes Figure 5 Enlarged view of section C.

[0028] Figure 7 yes Figure 5 Enlarged view of section D in the middle.

[0029] Figure 8 This is an exploded view of the first telescopic rod of this utility model.

[0030] Explanation of reference numerals in the attached drawings: 1. Steel arch frame; 2. Base; 21. Adjustment groove; 22. Guide hole; 221. Slide groove; 23. Clearance hole; 24. Slide hole; 25. Inclined hole; 3. Adjustment rod; 31. Adjustment shaft; 32. Adjustment seat; 321. Sliding block; 33. Adjustment ring; 34. Hanging rod; 35. Nut; 4. Support frame; 41. Support seat; 42. Support ball; 43. Support rod; 44. Support plate; 45. Second telescopic rod; 451. Rod cylinder; 452. Screw; 453. Adapter; 454. Ear plate; 455. First adapter shaft; 456. Second adapter shaft; 5. First telescopic rod; 51. Rod sleeve; 511. Annular groove; 52. Rod core; 53. Limiting rod; 54. Connecting rod; 6. Gear; 7. Rack; 71. Straight groove. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1-8 This application will be described in further detail.

[0032] This application discloses a hydraulic tunnel excavation support structure.

[0033] Reference Figures 1-8 A hydraulic tunnel excavation support structure includes a steel arch frame 1, and further includes:

[0034] Two bases 2, each base 2 has an adjustment groove 21 on its upper side, and each of the two opposite groove walls of the adjustment groove 21 has two guide holes 22. The two guide holes 22 on the same groove wall extend obliquely and move away from each other from bottom to top.

[0035] Four adjusting rods 3 are arranged in pairs in two adjusting slots 21, and the two ends of each adjusting rod 3 are respectively adapted to and slidably connected to two opposite guide holes 22;

[0036] Two support frames 4, the lower ends of the two support frames 4 are respectively adapted to and slidably connected to two adjustment slots 21, and the upper ends are respectively fixedly connected to both ends of the steel arch frame 1, and the lower sides of the two support frames 4 abut against the corresponding two adjustment rods 3.

[0037] Two linear drive assemblies are mounted on two bases 2 respectively, and the drive ends of the two linear drive assemblies are simultaneously connected to the corresponding two adjusting rods 3.

[0038] During the installation of the steel arch frame 1, the base 2 is first installed in the positioning position, and the two support frames 4 slide the two base 2 respectively. The steel arch frame 1 is then hoisted and its two ends are pressed down onto the two support frames 4 to form a pre-installation. The height of the two ends of the steel arch frame 1 is observed to see if it is correct. If it is incorrect, the two adjusting rods 3 can be moved simultaneously by the linear drive assembly at the lower end. The two adjusting rods 3 move obliquely upward under the guidance of the corresponding guide hole 22, and at the same time push the corresponding support frame 4 to move upward. This adjusts the support height of the corresponding support frame 4 on the end of the steel arch frame 1, thus improving the technical problem in the prior art that it is not convenient to adjust the support height of the two ends of the steel arch frame 1 and cannot ensure that the two ends of the steel arch frame 1 are at the same support height.

[0039] After the adjustment is in place, the two support frames 4 are welded and fixed to the two ends of the steel arch frame 1, thus completing the installation of the steel arch frame 1, after which other operations can be carried out.

[0040] During installation, the steel arch frame 1 can be hoisted to the predetermined position via the steel arch frame installation platform, so that both ends of the steel arch frame 1 are pressed down on the two support frames 4 respectively.

[0041] The adjustment groove 21 can be a cylindrical groove or a polygonal groove. Preferably, the adjustment groove 21 is a polygonal groove, such as a rectangular groove, to prevent the support frame 4 from rotating during vertical movement relative to the base 2, which would cause the support to be unstable.

[0042] When observing whether the heights at both ends of the steel arch frame 1 are correct, measurements can be taken using equipment known to those skilled in the art, such as a level, total station, laser rangefinder, infrared level measuring instrument, or vibrating wire sensor.

[0043] Reference Figures 2-8 The two opposite walls of the adjusting groove 21 are provided with clearance holes 23 located between the two corresponding guide holes 22; both linear drive assemblies include gears 6, racks 7 and two first telescopic rods 5. Each first telescopic rod 5 includes a rod sleeve 51 and two rod cores 52. The two ends of the rod sleeve 51 are provided with internal threads with opposite directions of rotation. One end of the two rod cores 52 is threaded to the two ends of the rod sleeve 51, and the other end of the two rod cores 52 is fixedly connected to the corresponding adjusting rods 3. The gears 6 are coaxially fixedly connected to the rod sleeves 51. The rack 7 meshes with the two gears 6 at the same time, and its two ends extend out from the two clearance holes 23 respectively.

[0044] When the corresponding two adjusting rods 3 are driven by the linear drive assembly at the corresponding position to move obliquely upward under the guidance of the corresponding guide hole 22, the rack 7 is pulled by applying force to the end of the rack 7 extending out of the clearance hole 23, so that the corresponding two gears 6 rotate at the same time, driving the two rod sleeves 51 to rotate at the same time, so that the corresponding two rod cores 52 move in opposite directions to push the two adjusting rods 3.

[0045] During the process of the adjusting rod 3 being pushed, the gear 6, rack 7 and the two first telescopic rods 5 move upward synchronously. The rack 7 moves upward within the clearance hole 23. In this embodiment, the operator can manually adjust the position of the rack 7 to maintain the meshing of the rack 7 and the gear 6.

[0046] In addition, in this embodiment, once the adjustment is complete, the operator can remove the rack 7 from the clearance hole 23 and recycle it, thereby reducing costs.

[0047] Reference Figure 3 and Figure 6 Each sleeve 51 has an annular groove 511 coaxially formed on its side wall, and each first telescopic rod 5 also includes a limiting rod 53 that is vertically slidably connected to the base 2.

[0048] The rod sleeve 51 and the base 2 are connected by a limiting rod 53 to prevent the rod sleeve 51 from moving axially during rotation. Based on the above embodiment, the base 2 has a through-hole 24 that connects to the adjusting groove 21, and the lower end of the limiting rod 53 is adapted to and slidably connected to the through-hole 24.

[0049] The side wall of the rack 7 is provided with a straight groove 71, and each limiting rod 53 is fixedly connected to a connecting rod 54. The end of each connecting rod 54 is adapted to and slidably connected to the straight groove 71.

[0050] The rack 7 is always engaged with the two gears 6 by connecting the two rods 54, avoiding the need to re-engage the rack 7 after it disengages from the gears 6. The linear slot 71 passes through the rack 7 to allow the rack 7 to be completely extracted and recycled.

[0051] Reference Figures 5-7 Each of the four adjusting rods 3 includes an adjusting shaft 31 and two adjusting seats 32 that are rotatably connected to both ends of the adjusting shaft 31. The rod part of each adjusting shaft 31 abuts against the lower side of the support frame 4 and is driven to the drive end of the corresponding linear drive assembly. Each adjusting seat 32 is adapted to and slidably connected to the corresponding guide hole 22.

[0052] When the corresponding two adjusting rods 3 are driven by the linear drive assembly at the corresponding position to move obliquely upward under the guidance of the corresponding guide hole 22, the adjusting seat 32 slides in the guide hole 22, and the rod part of each adjusting shaft 31 remains in contact with the lower side of the support frame 4, so that the support frame 4 moves vertically upward relative to the base 2, thereby realizing the adjustment of the height of the end of the steel arch frame 1.

[0053] Based on the above embodiments, each guide hole 22 has a groove 221 on its hole wall, and each adjustment seat 32 is fixedly connected to the slider 321 that is adapted to and slidably connected to the corresponding groove 221, so as to limit the sliding of the slider 321 by the groove 221, so that the adjustment seat 32 is detached from the base 2.

[0054] Each of the four adjusting rods 3 also includes multiple adjusting rings 33. Each adjusting ring 33 is spaced apart from the corresponding adjusting shaft 31 and is coaxially rotatably connected to the corresponding adjusting shaft 31. The adjusting shaft 31 abuts against the lower side of the support frame 4 through each adjusting ring 33.

[0055] As each adjusting shaft 31 is pushed and moves relative to the support frame 4, each adjusting ring 33 abuts against the lower side of the support frame 4 and rotates adaptively under the action of friction, forming rolling friction and reducing the resistance to pushing each adjusting shaft 31.

[0056] In this embodiment, each adjusting ring 33 can be a bearing, with the inner ring of the bearing coaxially fixedly connected to the adjusting shaft 31 and the outer ring abutting against the lower side of the support frame 4.

[0057] Reference Figure 5 The side wall of the base 2 has four oblique holes 25, which are connected to the guide holes 22 one by one, and the holes of the four oblique holes 25 are parallel to the inclined direction of the corresponding guide holes 22. Each of the four adjusting rods 3 also includes two hanging rods 34 and multiple nuts 35. One end of each hanging rod 34 is fixedly connected to the corresponding adjusting seat 32, and each nut 35 is threadedly connected to the other end of each hanging rod 34 and abuts against the base 2.

[0058] When each adjusting shaft 31 is pushed and moves upward along the guide hole 22, it pushes each hanging rod 34 to move. After the height of the support frame 4 is adjusted to the correct position, each nut 35 is rotated and pressed against the base 2. The corresponding adjusting shaft 31 is hoisted by the nut 35 and the hanging rod 34 to prevent the adjusting shaft 31 from moving downward under the gravity of the steel arch frame 1 and the support frame 4, thus preventing the failure of the support for the steel arch frame 1 and the support frame 4.

[0059] Reference Figure 2 , Figure 5 as well as Figure 7Both support frames 4 include a support base 41 that is adapted and slidably connected to the corresponding support base 41 at its lower end, a support ball 42 that is rotatably connected to the upper end of the support base 41, a support rod 43 that is fixedly connected to the support ball 42 at its lower end, and a support plate 44 that is fixedly connected to the upper end of the support rod 43 at its lower end. The two ends of the steel arch frame 1 are respectively fixedly connected to the upper ends of the two support plates 44. Both support frames 4 also include a second telescopic rod 45. The second telescopic rod 45 is vertically arranged and its two ends are rotatably connected to the corresponding support base 41 and support plate 44 respectively. The vertical plane formed by the axis of the second telescopic rod 45 and the center of the corresponding support ball 42 is perpendicular to the plane where the steel arch frame 1 is located.

[0060] After the height of both ends of the steel arch frame 1 is adjusted to the correct position, the support plate 44, support rod 43 and support ball 42 can be rotated relative to the support seat 41 by extending and retracting the second telescopic rod 45, causing the plane on which the steel arch frame 1 is located to change angle, so that the steel arch frame 1 is perpendicular to the centerline of the tunnel, thereby improving the stability of the structure.

[0061] Both second telescopic rods 45 include a rod cylinder 451 whose lower end is rotatably connected to the support base 41, a screw 452 whose lower end is threadedly connected to the rod cylinder 451, and an adapter 453 whose lower end is coaxially rotatably connected to the upper end of the screw 452. The upper end of the adapter 453 is rotatably connected to the support plate 44.

[0062] When adjusting the length of the second telescopic rod 45, a force can be applied to the screw 452, causing the screw 452 to move relative to the rod cylinder 451, thereby completing the length adjustment of the second telescopic rod 45. During the adjustment process, the rod cylinder 451 changes its tilt angle relative to the support base 41, and the screw 452 and the adapter 453 together change their tilt angle relative to the support plate 44.

[0063] Both second telescopic rods 45 also include four ear plates 454 that are fixedly connected in pairs to the corresponding support base 41 and support plate 44. The lower end of the rod tube 451 is fixedly connected to a first adapter shaft 455 that is rotatably connected to the two corresponding ear plates 454 at both ends. The upper end of the adapter 453 is rotatably connected to a second adapter shaft 456 that is rotatably connected to the two corresponding ear plates 454 at both ends.

[0064] When the screw 452 moves relative to the barrel 451, a relative rotation occurs between the screw 452 and the adapter 453, and both the first adapter shaft 455 and the second adapter shaft 456 rotate relative to their respective lugs 454. The side wall of the second adapter shaft 456 and the lower end of the adapter 453 are both provided with stepped holes. Both ends of the adapter 453 are T-shaped and are rotatably connected to the screw 452 and the second adapter shaft 456 through the stepped holes.

[0065] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A hydraulic tunnel excavation support structure, comprising a steel arch frame (1), characterized in that: Also includes: Two bases (2), each of the two bases (2) has an adjustment groove (21) on its upper side, and each of the two opposite groove walls of the adjustment groove (21) has two guide holes (22), and the two guide holes (22) on the same groove wall extend obliquely and move away from each other from bottom to top; Four adjusting rods (3) are arranged in pairs in the two adjusting grooves (21), and the two ends of each adjusting rod (3) are respectively adapted to and slidably connected to the two opposite guide holes (22). Two support frames (4), the lower ends of the two support frames (4) are respectively adapted to and slidably connected to the two adjustment slots (21), and the upper ends are respectively fixedly connected to the two ends of the steel arch frame (1), and the lower sides of the two support frames (4) abut against the corresponding two adjustment rods (3). Two linear drive assemblies are respectively mounted on two bases (2), and the drive ends of the two linear drive assemblies are simultaneously connected to the corresponding two adjusting rods (3).

2. The hydraulic tunnel excavation support structure according to claim 1, characterized in that: The two opposite walls of the adjustment groove (21) are provided with clearance holes (23) located between the two corresponding guide holes (22); the two sets of linear drive assemblies each include a gear (6), a rack (7) and two first telescopic rods (5), each of the first telescopic rods (5) includes a rod sleeve (51) and two rod cores (52), the two ends of the rod sleeve (51) are provided with internal threads with opposite directions of rotation, one end of the two rod cores (52) is threaded to the two ends of the rod sleeve (51) respectively, the other end of the two rod cores (52) is fixedly connected to the corresponding adjustment rod (3), the gear (6) is coaxially fixedly connected to the rod sleeve (51), the rack (7) meshes with the two gears (6) at the same time, and its two ends extend from the two clearance holes (23) respectively.

3. The hydraulic tunnel excavation support structure according to claim 2, characterized in that: Each of the rod sleeves (51) has an annular groove (511) coaxially formed on its side wall, and each of the first telescopic rods (5) also includes a limiting rod (53) that is vertically slidably connected to the base (2).

4. The hydraulic tunnel excavation support structure according to claim 3, characterized in that: The rack (7) has a straight groove (71) on its side wall. Each of the limiting rods (53) is fixedly connected to a connecting rod (54). The ends of each connecting rod (54) are adapted to and slidably connected to the straight groove (71).

5. The hydraulic tunnel excavation support structure according to claim 1, characterized in that: Each of the four adjusting rods (3) includes an adjusting shaft (31) and two adjusting seats (32) rotatably connected to both ends of the adjusting shaft (31). The rod portion of each adjusting shaft (31) abuts against the lower side of the support frame (4) and is driven to the driving end of the corresponding linear drive assembly. Each adjusting seat (32) is adapted to and slidably connected to the corresponding guide hole (22).

6. The hydraulic tunnel excavation support structure according to claim 5, characterized in that: Each of the four adjusting rods (3) also includes multiple adjusting rings (33), each adjusting ring (33) is spaced apart from the corresponding adjusting shaft (31), and is coaxially rotatably connected to the corresponding adjusting shaft (31). The adjusting shaft (31) abuts against the lower side of the support frame (4) through each adjusting ring (33).

7. The hydraulic tunnel excavation support structure according to claim 5, characterized in that: The base (2) has four through-holes (25) on its side wall. The four through-holes (25) are connected to the guide holes (22) one by one, and the holes of the four through-holes (25) are inclined in a direction parallel to the corresponding guide holes (22). The four adjusting rods (3) also include two hanging rods (34) and multiple nuts (35). One end of each hanging rod (34) is fixedly connected to the corresponding adjusting seat (32), and each nut (35) is threaded to the other end of each hanging rod (34) and abuts against the base (2).

8. A hydraulic tunnel excavation support structure according to any one of claims 1-7, characterized in that: Both of the support frames (4) include a support seat (41) adapted and slidably connected to the corresponding support seat (41) at the lower end, a support ball (42) rotatably connected to the upper end of the support seat (41), a support rod (43) fixedly connected to the support ball (42) at the lower end, and a support plate (44) fixedly connected to the upper end of the support rod (43) at the lower end. The two ends of the steel arch frame (1) are respectively fixedly connected to the upper ends of the two support plates (44). Both of the support frames (4) also include a second telescopic rod (45). The second telescopic rod (45) is vertically arranged and its two ends are rotatably connected to the corresponding support seat (41) and the support plate (44) respectively. The vertical plane formed by the axis of the second telescopic rod (45) and the center of the corresponding support ball (42) is perpendicular to the plane where the steel arch frame (1) is located.

9. A hydraulic tunnel excavation support structure according to claim 8, characterized in that: Both of the second telescopic rods (45) include a rod cylinder (451) whose lower end is rotatably connected to the support base (41), a screw (452) whose lower end is threadedly connected to the rod cylinder (451), and an adapter (453) whose lower end is coaxially rotatably connected to the upper end of the screw (452). The upper end of the adapter (453) is rotatably connected to the support plate (44).

10. A hydraulic tunnel excavation support structure according to claim 9, characterized in that: Both of the second telescopic rods (45) also include four ear plates (454) that are fixedly connected in pairs to the corresponding support base (41) and support plate (44). The lower end of the rod tube (451) is fixedly connected to a first adapter shaft (455) that is rotatably connected to the two ear plates (454) respectively. The upper end of the adapter (453) is rotatably connected to a second adapter shaft (456) that is rotatably connected to the two ear plates (454) respectively.

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