Aluminum alloy drilling positioning clamp

Abstract

The utility model discloses an aluminum alloy drilling positioning clamp, and relates to the technical field of aluminum alloy machining. The device comprises a base, a rotating disc is rotationally arranged on the base, a mounting roller is arranged on the rotating disc, a limiting ring, a plurality of penetrating holes and a locking piece are arranged on the mounting roller, the mounting roller is sleeved with tubular aluminum alloy, one end of the tubular aluminum alloy abuts against and is in lap joint with the limiting ring, and the locking piece acts on the tubular aluminum alloy and locks or unlocks the tubular aluminum alloy; the base is provided with a positioning plate and a locking portion acting on the rotating disc, the positioning plate is provided with positioning holes which are the same as the penetrating holes in number and correspond to the penetrating holes in a one-to-one mode, and the rotating disc is driven to rotate through the locking portion to lock or unlock the rotating disc. After the tubular aluminum alloy is fixed, the tubular aluminum alloy does not need to be frequently disassembled and assembled to adjust the position, circumferential drilling can be conducted on the tubular aluminum alloy, the drilling efficiency is improved while operation is convenient, and therefore the tubular aluminum alloy drilling device is more practical.

Description

Technical Field

[0001] This application relates to the technical field of aluminum alloy processing, and specifically relates to an aluminum alloy drilling positioning fixture. Background Art

[0002] Aluminum alloy is one of the most widely used non-ferrous metal structural materials in industry and has been widely used in aviation, aerospace, automotive, machinery manufacturing, shipbuilding, and chemical industries. During the processing of aluminum alloy, drilling is usually required. When drilling, a positioning fixture is needed to fix the aluminum alloy. After the existing positioning fixture fixes the tubular aluminum alloy, if circumferential drilling is to be carried out on the tubular aluminum alloy, it is usually necessary to frequently disassemble and adjust the position of the tubular aluminum alloy, which is rather troublesome to operate and also reduces the drilling efficiency. Therefore, an aluminum alloy drilling positioning fixture is proposed. Utility Model Content

[0003] The purpose of this application is to solve the technical problem that if circumferential drilling is to be carried out on a tubular aluminum alloy, it is usually necessary to frequently disassemble and adjust the position of the tubular aluminum alloy, which is rather troublesome to operate and also reduces the drilling efficiency. This application provides an aluminum alloy drilling positioning fixture.

[0004] This application specifically adopts the following technical solutions to achieve the above purpose:

[0005] An aluminum alloy drilling positioning fixture, comprising:

[0006] A base, on which a turntable is rotatably arranged. An installation roller is arranged on the turntable. A limiting ring, a plurality of through holes, and a locking member are arranged on the installation roller. The tubular aluminum alloy is sleeved on the installation roller and one end abuts and overlaps with the limiting ring. The locking member acts on the tubular aluminum alloy to lock or unlock it. The through holes include a plurality of connected through holes. A positioning plate and a locking portion acting on the turntable are arranged on the base. The positioning plate is provided with positioning holes that are the same in number as and correspond one by one to the through holes. The turntable is driven to rotate and locked or unlocked by the locking portion.

[0007] Further, the locking member includes a fixing rod arranged on the installation roller. A fixing ring is detachably arranged on the fixing rod. A tapered ring is arranged on the fixing ring. The tapered ring is slidably matched with the installation roller and abuts and overlaps with the tubular aluminum alloy.

[0008] Further, a central hole is provided in the fixing ring. A convex block is arranged in the central hole. A threaded section and a groove are arranged on the fixing rod. The fixing rod is inserted into the central hole in a plug-in fit. The convex block is inserted into the groove in a plug-in fit. A locking nut that abuts and overlaps with the fixing ring is threadedly arranged on the threaded section.

[0009] Further, the installation roller is detachably arranged on the turntable, and the positioning plate is detachably arranged on the base.

[0010] Further, a plug-in slot is formed in the turntable, a plug-in block that is pluggably engaged with the plug-in slot is provided on the mounting roller, the plug-in block is detachably connected to the turntable by a bolt member, and the positioning plate is detachably connected to the base by a plurality of bolt portions.

[0011] Further, the locking portion includes a fixing plate provided on the base, a plurality of concave holes are formed in the fixing plate, a movable rod is movably provided on the fixing plate, a convex column that is pluggably engaged with the concave holes is provided on the movable rod, a movable groove is formed in the turntable, one end of the movable rod extends into the movable groove and is provided with a limiting plate that is slidably engaged therewith, and a return spring is provided between the limiting plate and the movable groove.

[0012] Further, a transverse moving frame is slidably provided on the base, a threaded rod that is threaded through the transverse moving frame is rotatably provided on the base, and a supporting member that acts on the fixing ring and provides rolling support or releases rolling support for it is provided on the transverse moving frame.

[0013] Further, the supporting member includes a supporting plate that is spaced apart from the transverse moving frame, two sliders are slidably provided on the transverse moving frame, a forward and reverse lead screw is rotatably provided on the transverse moving frame, the two sliders are respectively threadedly engaged with the forward and reverse threaded sections of the forward and reverse lead screw, a connecting rod is hinged to the slider, the free end of the connecting rod is hinged to the supporting plate, and a plurality of supporting wheels that are all in rolling contact with the fixing ring are rotatably provided on the supporting plate.

[0014] The beneficial effects of the present application are as follows:

[0015] After the tubular aluminum alloy is fixed in the present application, it is not necessary to frequently disassemble and assemble the tubular aluminum alloy to adjust its position, and the tubular aluminum alloy can be drilled circumferentially. It is convenient to operate and improves the drilling efficiency at the same time, so it is more practical. Description of the Drawings

[0016] Figure 1 is a three-dimensional structure diagram of the present application;

[0017] Figure 2 is a three-dimensional structure diagram of a part of the present application;

[0018] Figure 3 is an exploded three-dimensional structure diagram of a part of the present application;

[0019] Figure 4 is a Figure 3 three-dimensional sectional view of the present application;

[0020] Figure 5 is a three-dimensional structure diagram of a part of the present application;

[0021] Figure 6 is a Figure 5Stereoscopic sectional view;

[0022] Figure 7 is the enlarged view of part A in the present application; Figure 6

[0023] Figure 8 is the enlarged view of part B in the present application; Figure 6

[0024] Figure 9 is the stereoscopic view of part of the structure of the present application.

[0025] Reference numerals: 1, base; 2, turntable; 3, mounting roller; 4, limiting ring; 5, through hole; 6, positioning plate; 7, positioning hole; 8, fixing rod; 9, fixing ring; 10, tapered ring; 11, central hole; 12, convex block; 13, threaded section; 14, groove; 15, locking nut; 16, insertion slot; 17, insertion block; 18, fixing plate; 19, concave hole; 20, movable rod; 21, convex column; 22, movable slot; 23, limiting plate; 24, return spring; 25, transverse moving frame; 26, threaded rod; 27, support plate; 28, slider; 29, positive and negative lead screw; 30, connecting rod; 31, support wheel. Detailed implementation manners

[0026] For the purpose of making the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

[0027] As Figures 1-7 shown, a kind of aluminum alloy drilling positioning fixture proposed in an embodiment of the present application includes:

[0028] A base 1, on which a turntable 2 is rotatably arranged. The turntable 2 is in the vertical direction. An installation roller 3 is arranged on the turntable 2. The installation roller 3 is in the horizontal direction. A limiting ring 4, a plurality of through holes and a locking member are arranged on the installation roller 3. The limiting ring 4 is in the vertical direction and is fixedly arranged on the installation roller 3. The plurality of through holes are arranged in an array along the horizontal direction. A tubular aluminum alloy is sleeved on the installation roller 3 and one end thereof abuts and laps with the limiting ring 4. The locking member acts on the tubular aluminum alloy and locks or unlocks it. The through holes include a plurality of communicating through holes 5. The through holes 5 are perpendicular to the axis of the installation roller 3. The plurality of through holes 5 are arranged in an annular array. A positioning plate 6 and a locking portion acting on the turntable 2 are arranged on the base 1. The positioning plate 6 is in the horizontal direction. A positioning hole 7 with the same number and one-to-one correspondence as the through holes is formed on the positioning plate 6. The plurality of positioning holes 7 are all in the vertical direction and are arranged in an array along the horizontal direction. The turntable 2 is driven to rotate by the locking portion and is locked or unlocked;

[0029] ​​In the initial state, the turntable 2 is locked by the locking part, and the through hole 5 corresponds to the positioning hole 7. When in use, the tubular aluminum alloy is sleeved on the mounting roller 3 in the horizontal direction, one end of the tubular aluminum alloy abuts and overlaps with the limit ring 4, and the tubular aluminum alloy is locked by the locking member. During this process, the tubular aluminum alloy will be coaxially distributed with the mounting roller 3 to fix the tubular aluminum alloy. When drilling, the rotating drill bit moves downward. During this process, the drill bit first passes through one of the positioning holes 7, then contacts the tubular aluminum alloy and drills a hole in the tubular aluminum alloy. After that, the drill bit passes through one of the through holes 5 and contacts the tubular aluminum alloy again, drilling another hole in the tubular aluminum alloy. Finally, the rotating drill bit is moved upward to the initial position. When circular drilling needs to be performed on the tubular aluminum alloy, the turntable 2 is unlocked by the locking part and driven to rotate, driving the fixed tubular aluminum alloy to rotate together until the through hole 5 corresponds to the positioning hole 7, and then the turntable 2 is locked by the locking part. Repeat the above operations during drilling. In this way, circular drilling of the tubular aluminum alloy can be achieved without frequently disassembling and adjusting the position of the tubular aluminum alloy, which is convenient to operate and improves the drilling efficiency at the same time. When the drilling of the tubular aluminum alloy is completed, the tubular aluminum alloy is unlocked by the locking member, and the tubular aluminum alloy is separated from the mounting roller 3;

[0030] In summary, after the tubular aluminum alloy is fixed in this application, circular drilling can be performed on the tubular aluminum alloy without frequently disassembling and adjusting the position of the tubular aluminum alloy, which is convenient to operate and improves the drilling efficiency at the same time. Therefore, it is more practical.

[0031] As Figures 3-4 shown, in some embodiments, the locking member includes a fixing rod 8 provided on the mounting roller 3. The fixing rod 8 is in the horizontal direction and is fixed at one end of the mounting roller 3. A fixing ring 9 is detachably provided on the fixing rod 8. The fixing ring 9 is in the vertical direction. A conical ring 10 is provided on the fixing ring 9. The conical ring 10 is in the vertical direction and is fixed on the fixing ring 9. The conical ring 10 is slidably engaged with the mounting roller 3 and abuts and overlaps with the tubular aluminum alloy. The conical ring 10 is slidably engaged with the mounting roller 3 in the horizontal direction;

[0032] Referring to the above, in the initial state, the fixing ring 9 is not installed on the fixing rod 8. When in use, the tubular aluminum alloy is horizontally sleeved on the installation roller 3, so that one end of the tubular aluminum alloy is in contact with the limit ring 4 and overlapped, and the fixing ring 9 is installed on the fixing rod 8, and the conical ring 10 is in contact with the tubular aluminum alloy and overlapped. When the inner diameter of the tubular aluminum alloy is the same as the outer diameter of the installation roller 3, the tubular aluminum alloy is locked by the conical ring 10. When the inner diameter of the tubular aluminum alloy is larger than the outer diameter of the installation roller 3, the conical ring 10 will slide with the installation roller 3. Through the inclined transition effect of the conical ring 10, the tubular aluminum alloy is moved to be coaxially distributed with the installation roller 3, and the tubular aluminum alloy is locked by the conical ring 10. Conversely, when the tubular aluminum alloy is drilled, the fixing ring 9 is removed from the fixing rod 8 to unlock the tubular aluminum alloy.

[0033] like Figure 3 As shown, in some embodiments, a center hole 11 is provided on the fixing ring 9, and the center hole 11 is provided along the length direction of the fixing ring 9. A protrusion 12 is provided in the center hole 11, and the protrusion 12 is fixed in the center hole 11. A threaded section 13 and a groove 14 are provided on the fixing rod 8, and the threaded section 13 and the groove 14 are both provided along the length direction of the fixing rod 8. The fixing rod 8 is plugged in with the center hole 11, and the protrusion 12 is plugged in with the groove 14. A locking nut 15 that contacts and overlaps with the fixing ring 9 is threadedly provided on the threaded section 13;

[0034] Referring to the above, when in use, the fixing ring 9 is moved horizontally to the fixing rod 8. During this process, the fixing rod 8 is plugged into the center hole 11, and the protrusion 12 is plugged into the groove 14. Then the locking nut 15 is tightened onto the threaded section 13 until the fixing ring 9 moves to the extreme position. The locking nut 15 and the fixing ring 9 are in contact and overlapped to achieve the installation of the fixing ring 9. Conversely, the locking nut 15 is loosened away from the threaded section 13, so that the fixing ring 9 moves horizontally away from the fixing rod 8. During this process, the fixing rod 8 withdraws from the center hole 11, and the protrusion 12 withdraws from the groove 14 to achieve the removal of the fixing ring 9.

[0035] like Figures 2-5 As shown, in some embodiments, the mounting roller 3 is detachably disposed on the turntable 2, and the positioning plate 6 is detachably disposed on the base 1;

[0036] Referring to the above, when in use, the detachable setting of the mounting roller 3 facilitates replacement of mounting rollers 3 of different sizes, thereby being suitable for drilling requirements of tubular aluminum alloys of different sizes. The detachable setting of the positioning plate 6 facilitates replacement of positioning plates 6 of different sizes, thereby corresponding to mounting rollers 3 of different sizes, thereby improving flexibility and applicability of use.

[0037] like Figures 2-5As shown, in some embodiments, a plugging slot 16 is formed in the turntable 2, and a plugging block 17 which is in plugging fit with the plugging slot 16 is arranged on the mounting roller 3. The plugging block 17 is fixedly arranged at the other end of the mounting roller 3. An installation hole communicating with the plugging slot 16 is formed in the plugging block 17. The plugging block 17 and the turntable 2 are detachably connected by a bolt member. The bolt member includes a mounting screw rod and a mounting screw barrel in threaded fit. The mounting screw rod is movably inserted into the plugging slot 16 and is in plugging fit with the installation hole. The mounting screw barrel is tightened on the mounting screw rod and abuts against and lapped with the turntable 2. The positioning plate 6 and the base 1 are detachably connected by a plurality of bolt parts. A connection hole which is the same in number as and corresponds to the bolt parts one by one is formed in the positioning plate 6. The bolt part includes a connection screw rod and a connection screw barrel in threaded fit. The connection screw rod is vertically arranged and fixedly arranged on the base 1. The connection screw rod is in plugging fit with the connection hole. The connection screw barrel is tightened on the connection screw rod and abuts against and lapped with the positioning plate 6;

[0038] Referring to the above, in the initial state, the mounting roller 3 is installed on the turntable 2. The plugging block 17 is completely located in the plugging slot 16. The plugging block 17 and the turntable 2 are fixed by the bolt member. When the turntable 2 rotates, the mounting roller 3 is driven to rotate together through the cooperation of the plugging block 17 and the plugging slot 16. The positioning plate 6 is installed on the base 1. The positioning plate 6 and the base 1 are fixed by a plurality of bolt parts. When it is necessary to disassemble the mounting roller 3, the fixing between the plugging block 17 and the turntable 2 is released by the bolt member, so that the mounting roller 3 moves away from the turntable 2, and the plugging block 17 withdraws from the plugging slot 16. When the mounting roller 3 is installed, the plugging block 17 is completely located in the plugging slot 16, and the plugging block 17 and the turntable 2 are fixed by the bolt member. When it is necessary to disassemble the positioning plate 6, the fixing between the positioning plate 6 and the base 1 is released by a plurality of bolt parts, so that the positioning plate 6 moves away from the base 1. When the positioning plate 6 is installed, the positioning plate 6 is located on the base 1, and the positioning plate 6 and the base 1 are fixed by a plurality of bolt parts.

[0039] As Figures 5-8As shown, in some embodiments, the locking portion includes a fixing plate 18 provided on the base 1. The fixing plate 18 is fixedly provided on the base 1. A plurality of concave holes 19 are formed in the fixing plate 18. The plurality of concave holes 19 are all in the horizontal direction and are distributed in an annular array. A movable rod 20 is movably provided on the fixing plate 18. The movable rod 20 moves in the horizontal direction. A convex column 21 that is inserted and matched with the concave hole 19 is provided on the movable rod 20. The convex column 21 is in the horizontal direction and is fixedly provided on the movable rod 20. A movable groove 22 is formed in the turntable 2. The movable groove 22 is formed along the length direction of the turntable 2. One end of the movable rod 20 extends into the movable groove 22 and is provided with a limiting plate 23 that is slidably matched with it. The limiting plate 23 is fixedly connected to the movable rod 20. A return spring 24 is provided between the limiting plate 23 and the movable groove 22. The return spring 24 is in the horizontal direction. A scale disk in the vertical direction is fixedly provided on the fixing plate 18. The other end of the movable rod 20 is fixedly provided with a pointer disk in the vertical direction and corresponding to the scale disk;

[0040] Referring to the above, in the initial state, the return spring 24 is in a natural state. The movable rod 20, the limiting plate 23, and the pointer disk are all in the initial positions. The convex column 21 is inserted into one of the concave holes 19. At this time, the turntable 2 cannot rotate, so as to lock the turntable 2. When in use, drive the pointer disk to move to the limit position and close to the scale disk, drive the movable rod 20 to move to the limit position together. The convex column 21 exits the concave hole 19. The limiting plate 23 slides to the limit position in the movable groove 22. The return spring 24 is compressed, so as to unlock the turntable 2. Then drive the pointer disk to rotate, drive the movable rod 20 and the limiting plate 23 to rotate together. Through the cooperation of the limiting plate 23 and the movable groove 22, drive the turntable 2 to rotate. Through the cooperation of the pointer disk and the scale disk, it is convenient to know the rotation angle, so as to drive the turntable 2 to rotate. Finally, release the pointer disk. The return spring 24 returns to the natural state. The limiting plate 23, the movable rod 20, and the pointer disk move to the initial positions together. The convex column 21 is inserted into one of the concave holes 19. The turntable 2 cannot rotate, thus locking the turntable 2 again.

[0041] As Figure 9 shown, in some embodiments, a transverse movement frame 25 is slidably provided on the base 1. The transverse movement frame 25 slides in the horizontal direction. A threaded rod 26 that is threaded through the transverse movement frame 25 is rotatably provided on the base 1. The threaded rod 26 is in the horizontal direction. A support member that acts on the fixing ring 9 and provides rolling support or releases rolling support for it is provided on the transverse movement frame 25;

[0042] Referring to the above, when in use, by driving the threaded rod 26 to rotate, the transverse movement frame 25 slides in the horizontal direction due to the thread action, drives the support member to move together, and provides rolling support for the fixing ring 9 through the support member, thereby improving the use stability and preventing the tubular aluminum alloy from shaking during drilling.

[0043] AsFigure 9 As shown, in some embodiments, the support member includes a support plate 27 spaced apart from the transverse movement frame 25. The support plate 27 is in a horizontal direction and is vertically distributed with the transverse movement frame 25. Two sliders 28 are slidably arranged on the transverse movement frame 25. The sliders 28 slide in the horizontal direction. A forward and reverse lead screw 29 is rotatably arranged on the transverse movement frame 25. The forward and reverse lead screw 29 is in a horizontal direction. The two sliders 28 are respectively in threaded cooperation with the forward and reverse threaded sections 13 of the forward and reverse lead screw 29. A connecting rod 30 is hinged to the slider 28. The free end of the connecting rod 30 is hinged to the support plate 27. A plurality of support wheels 31 that are all in rolling contact with the fixed ring 9 are rotatably arranged on the support plate 27. The plurality of support wheels 31 are all in a vertical direction and are distributed in a circular array;

[0044] Referring to the above, in the initial state, the support plate 27 is close to the transverse movement frame 25, the two sliders 28 are away from each other, and the two connecting rods 30 both tend to be in a horizontal direction. When in use, the forward and reverse lead screw 29 is driven to rotate forward. The two sliders 28 respectively slide synchronously and reversely towards each other due to the action of the forward and reverse threads. The two connecting rods 30 respectively rotate synchronously and reversely around their respective hinge points until they both tend to be in a vertical direction, thereby driving the support plate 27 to move upward until the plurality of support wheels 31 are all in rolling contact with the fixed ring 9 to realize rolling support for the fixed ring 9. On the contrary, when the drilling is completed, the forward and reverse lead screw 29 is driven to rotate reversely. The two sliders 28 respectively slide synchronously and reversely away from each other due to the action of the forward and reverse threads. The two connecting rods 30 respectively rotate synchronously and reversely around their respective hinge points until they both tend to be in a horizontal direction, thereby driving the support plate 27 to move downward until the plurality of support wheels 31 are all away from the fixed ring 9 to facilitate the subsequent disassembly of the fixed ring 9, the tubular aluminum alloy, and the mounting roller 3.

[0045] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An aluminum alloy drilling positioning fixture, characterized in that: include: A base (1) is provided with a turntable (2) rotatably mounted thereon, a mounting roller (3) is provided on the turntable (2), a limit ring (4), a plurality of perforations and a locking member are provided on the mounting roller (3), a tubular aluminum alloy is sleeved on the mounting roller (3) and one end thereof is in contact with and overlaps the limit ring (4), the locking member acts on the tubular aluminum alloy and locks or unlocks it, the perforations include a plurality of interconnected through holes (5), a positioning plate (6) and a locking member acting on the turntable (2) are provided on the base (1), the positioning plate (6) is provided with positioning holes (7) having the same number as the perforations and corresponding to each other, and the turntable (2) is driven to rotate and be locked or unlocked by the locking member.

2. The aluminum alloy drilling positioning fixture according to claim 1, characterized in that: The locking member comprises a fixing rod (8) arranged on the installation roller (3), a fixing ring (9) being detachably arranged on the fixing rod (8), a cone ring (10) being arranged on the fixing ring (9), the cone ring (10) being slidably matched with the installation roller (3) and being in contact and overlapped with the tubular aluminum alloy.

3. The aluminum alloy drilling positioning fixture according to claim 2, characterized in that: The fixing ring (9) is provided with a center hole (11), a protrusion (12) is arranged in the center hole (11), a threaded section (13) and a groove (14) are arranged on the fixing rod (8), the fixing rod (8) and the center hole (11) are plugged together, the protrusion (12) and the groove (14) are plugged together, and a locking nut (15) is threadedly arranged on the threaded section (13) and is in contact with and overlapped with the fixing ring (9).

4. The aluminum alloy drilling positioning fixture according to claim 1, characterized in that: The installation roller (3) is detachably arranged on the turntable (2), and the positioning plate (6) is detachably arranged on the base (1).

5. The aluminum alloy drilling positioning fixture according to claim 4, characterized in that: The turntable (2) is provided with a plug-in slot (16), the installation roller (3) is provided with a plug-in block (17) plugged into and matched with the plug-in slot (16), the plug-in block (17) and the turntable (2) are detachably connected via bolts, and the positioning plate (6) and the base (1) are detachably connected via a plurality of bolts.

6. The aluminum alloy drilling positioning fixture according to claim 1, characterized in that: The locking portion comprises a fixed plate (18) arranged on the base (1), a plurality of recessed holes (19) being provided on the fixed plate (18), a movable rod (20) being movably provided on the fixed plate (18), a convex column (21) being provided on the movable rod (20) being plugged into and matched with the recessed holes (19), a movable groove (22) being provided on the turntable (2), one end of the movable rod (20) extending into the movable groove (22) and being provided with a limiting plate (23) slidably matched with the movable groove, and a return spring (24) being provided between the limiting plate (23) and the movable groove (22).

7. The aluminum alloy drilling positioning fixture according to claim 2, characterized in that: A transverse frame (25) is slidably arranged on the base (1), a threaded rod (26) is rotatably arranged on the base (1) and the thread penetrates the transverse frame (25), and a support member is arranged on the transverse frame (25) to act on the fixing ring (9) and provide rolling support or release the rolling support for the fixing ring (9).

8. The aluminum alloy drilling positioning fixture according to claim 7, characterized in that: The support member comprises a support plate (27) spaced apart from the transverse frame (25); two sliders (28) are slidably arranged on the transverse frame (25); a forward and reverse screw rod (29) is rotatably arranged on the transverse frame (25); the two sliders (28) are respectively threadedly matched with the forward and reverse threaded sections (13) of the forward and reverse screw rod (29); a connecting rod (30) is hinged on the slider (28); a free end of the connecting rod (30) is hinged on the support plate (27); a plurality of support wheels (31) are rotatably arranged on the support plate (27) and are all in rolling overlap with the fixing ring (9).

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