Extrusion device for aluminum alloy machining

Abstract

The invention relates to the technical field of aluminum alloy machining, in particular to an extrusion device for aluminum alloy machining, which comprises a base, a supporting column is fixedly connected to the base, a top seat is fixedly connected to the supporting column, an extrusion assembly is arranged on the base and the top seat, the extrusion assembly comprises a machining barrel, a support, a die hole, a sleeve, a telescopic rod and an extrusion seat, and a driving assembly is arranged on the top seat. A cutting assembly is arranged at the bottom of the machining barrel and comprises a first gear, a sliding rod, a cutting knife, a second spring, a wave ring, a limiting rod, a semicircular plate, a grinding plate and a third spring, a driving assembly is arranged on the top seat and comprises a hydraulic machine, the hydraulic machine is fixedly connected to the top seat, and a cooperation assembly is arranged on the machining barrel. In the extrusion forming process of the aluminum alloy profile, the aluminum alloy profile can be cut and segmented while being extruded, and the cutter can be switched, cooled and polished synchronously in the cutting process, so that the burden of the cutter is reduced, and the machining efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy processing, in particular to an extrusion device for aluminum alloy processing. Background Art

[0002] Extrusion is the main processing method for processing aluminum alloy raw materials into various profiles. Its main principle is to heat the aluminum alloy raw materials to a certain temperature to soften them, and then extrude the aluminum alloy through the die to continuously generate profiles with the same shape as the die.

[0003] The aluminum alloy profiles produced by extrusion are continuous. Therefore, in order to obtain aluminum alloy profiles, it is usually necessary to cut and segment the aluminum alloy profiles after they have cooled. However, in actual production, the extruded aluminum alloy profiles usually reach tens of meters, so the cutting and segmenting also needs to be performed dozens of times. During this process, the tool needs to be used continuously for dozens of times, which will put a heavy burden on the tool. Therefore, the tool needs to be changed frequently, which affects the continuity of aluminum alloy processing and reduces production efficiency. For this reason, an extrusion device for aluminum alloy processing is needed to solve this problem. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes an extrusion device for aluminum alloy processing, which can cut and segment the aluminum alloy profile while extruding it during the extrusion molding process of the aluminum alloy profile, and the tool can be switched, cooled and polished synchronously during the cutting process, thereby reducing the burden on the tool and improving processing efficiency.

[0005] The technical solution to achieve the purpose of the present invention is: an extrusion device for aluminum alloy processing, comprising a base, a pillar fixedly connected to the base, a top seat fixedly connected to the pillar, an extrusion assembly arranged on the base and the top seat, the extrusion assembly comprising a processing barrel, a bracket, a die hole, a sleeve, a telescopic rod and an extrusion seat, the bracket fixedly connected to the base, the processing barrel fixedly connected to the bracket, the die hole is opened at the bottom of the processing barrel, the sleeve fixedly connected to the top seat, the telescopic rod is slidably connected to the inside of the sleeve, the extrusion seat is fixedly connected to the telescopic rod, a driving assembly is arranged on the top seat, a cutting assembly is arranged at the bottom of the processing barrel, the cutting assembly comprises a first gear, a sliding rod, a cutting knife, a second spring, a wave ring, a limiting rod, a semicircular plate, a grinding plate and a third spring, the first gear is rotatably connected to the processing barrel, the sliding rod is slidably connected to the first gear On, the two cutting knives are fixedly connected to the sliding rod, the two second springs are respectively fixedly connected to the two ends of the sliding rod and between the first gear, the wave ring is fixedly connected to the bracket, the limit rod is fixedly connected to the sliding rod, the limit rod is slidably connected to the inner wall of the wave ring, the two semicircular plates are respectively fixedly connected to the bottom of the processing barrel and the bracket, the two grinding plates are respectively slidably connected to the inside of the two semicircular plates, the two third springs are respectively fixedly connected to the inner walls of the two semicircular plates and between the two grinding plates, a driving assembly is provided on the top seat, the driving assembly includes a hydraulic press, the hydraulic press is fixedly connected to the top seat, and a cooperative assembly is provided on the processing barrel, the cooperative assembly includes a rotating column and a second gear, the rotating column is rotatably connected to the base, the second gear is fixedly connected to the rotating column, the second gear is meshed with the first gear, and the hydraulic press cooperates with the second gear.

[0006] Preferably, the driving assembly further comprises a lifting column and a fixed plate, the lifting column is fixedly connected to the piston rod of the hydraulic press, a plurality of the fixed plates are fixedly connected to the lifting column, and the plurality of fixed plates are distributed in a linear array.

[0007] Preferably, the driving assembly also includes a connecting seat, a sliding seat and a first pawl, the connecting seat is fixedly connected to the extrusion seat, the sliding seat is slidably connected to the inside of the connecting seat, the first pawl is fixedly connected to the sliding seat, the first pawl extends outside the connecting seat, and the first pawl is engaged with the fixed plate.

[0008] Preferably, the driving assembly further comprises a pull rod and a first spring, wherein the pull rod is fixedly connected to the sliding seat and extends out of the connecting seat, and the first spring is fixedly connected between the sliding seat and the inner wall of the connecting seat.

[0009] Preferably, the cooperative component further comprises a cylinder and a support ring, wherein the support ring is fixedly connected to the processing barrel, and the cylinder is rotatably connected to the support ring.

[0010] Preferably, the cooperative component further comprises a ball head rod and a threaded groove, the ball head rod is fixedly connected to the lifting column, the threaded groove is formed on the inner wall of the cylinder, and the ball head rod is slidably connected to the inside of the threaded groove.

[0011] Preferably, the cooperative component further comprises a ratchet and a second pawl, wherein the ratchet is fixedly connected to the rotating column, and the second pawl is arranged on the inner wall of the cylinder, and the second pawl is meshed with the ratchet.

[0012] Compared with the prior art, the present invention has the following significant advantages:

[0013] First, in the present invention, by providing an extrusion assembly and a drive assembly, an aluminum alloy ingot for processing an aluminum alloy profile can be thrown into a processing barrel. After the hydraulic press is started, its piston rod will move up and down reciprocatingly, thereby driving the lifting column to move up and down. During the up and down movement of the lifting column, the fixed plate thereon will drive the first ratchet to move downward intermittently. The downward movement of the first ratchet will drive the extrusion seat to move downward until the extrusion seat enters the processing barrel and abuts against the aluminum alloy ingot. Then the extrusion seat continues to move downward intermittently. Each time it moves downward, the aluminum alloy ingot will be squeezed downward for a section. The extruded aluminum alloy ingot will pass through the die hole to form an aluminum alloy profile. Since the extrusion seat moves downward intermittently, the aluminum alloy profile will be extruded from the die hole for a section, then remain still for a period of time, and then the next section of the aluminum alloy profile will be extruded again.

[0014] Second: In the present invention, by setting a cooperative component, the ball head rod at the bottom end of the lifting column will also move up and down during the process of moving up and down. Since the ball head rod slides in the threaded groove and the cylinder is rotatably connected to the support ring, when the ball head rod moves up and down, the cylinder will also rotate accordingly. When the ball head rod moves downward with the lifting column, the cylinder and the second pawl at its bottom rotate, but at this time the second pawl will not drive the ratchet to rotate. At this time, the aluminum alloy profile is being extruded from the die hole, and when the lifting column drives the ball head rod to move upward, the cylinder rotates in the opposite direction. At this time, the second pawl will drive the ratchet to rotate, and the rotation of the ratchet will drive the rotating column and the second gear thereon to rotate.

[0015] Thirdly, in the present invention, a cutting assembly is provided so that when the second gear rotates, the first gear is driven to rotate, and the first gear rotates half a circle each time. During the process of the first gear rotating half a circle, the slide bar thereon will rotate accordingly. Since the wave ring is in a fixed state, when the slide bar and the first gear rotate, the limit rod on the slide bar will also move back and forth due to the inner wall of the wave ring being abutted. Therefore, the cutting knife on the slide bar will rotate to cut the aluminum alloy profile below the die hole. While cutting, the cutting knife will reciprocate with the slide bar to increase the friction between the cutting knife blade and the aluminum alloy profile, thereby making the aluminum alloy profile easier to cut. Since the cutting knife will rotate with the first gear and rotate half a circle each time, the two cutting knives will perform cutting work alternately. Among the two cutting knives, one cutting knife is responsible for cutting at a time, and the other can pass through two grinding plates for cooling and grinding. The two cutting knives perform cutting, cooling and grinding alternately, so that the cutting work can be carried out continuously, greatly reducing the need for frequent knife changes during the cutting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments:

[0017] Figure 1 The three-dimensional structure of the present invention is shown in FIG. Figure 1 ;

[0018] Figure 2 The three-dimensional structure of the present invention is shown in FIG. Figure 2 ;

[0019] Figure 3 It is a schematic diagram of the connection structure between the processing barrel and the cutting assembly in the present invention;

[0020] Figure 4 It is a schematic diagram of the connection structure between the first gear and the sliding rod in the present invention;

[0021] Figure 5 is a cross-sectional view of the internal structure of the present invention;

[0022] Figure 6 The present invention Figure 5 An enlarged view of the structure of part A is shown;

[0023] Figure 7 The present invention Figure 5 An enlarged view of the structure of part B is shown;

[0024] Figure 8 It is a schematic diagram of the structure of the cylinder and the thread groove in the present invention;

[0025] Fig. 9 It is a structural exploded diagram of the semicircular plate and the grinding plate in the present invention.

[0026] Description of reference numerals:

[0027] 1. Base; 2. Pillar; 3. Top seat; 4. Extrusion assembly; 41. Processing barrel; 42. Bracket; 43. Die hole; 44. Sleeve; 45. Telescopic rod; 46. Extrusion seat; 5. Driving assembly; 51. Hydraulic press; 52. Lifting column; 53. Fixed plate; 54. Connecting seat; 55. Sliding seat; 56. First pawl; 57. Pull rod; 58. First spring; 6. Cutting assembly; 61. First gear; 62. Slide rod; 63. Cutting knife; 64. Second spring; 65. Wave ring; 66. Limit rod; 67. Semicircular plate; 68. Grinding plate; 69. Third spring; 7. Cooperative assembly; 71. Cylinder; 72. Support ring; 73. Ball head rod; 74. Threaded groove; 75. Rotating column; 76. Second gear; 77. Ratchet; 78. Second pawl. DETAILED DESCRIPTION

[0028] The present invention is described in detail below, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention provides an extrusion device for aluminum alloy processing by improvement. The technical solution of the present invention is:

[0030] like Figure 1-Figure 9As shown, an extrusion device for aluminum alloy processing includes a base 1, a support 2 is fixedly connected to the base 1, a top seat 3 is fixedly connected to the support 2, an extrusion assembly 4 is arranged on the base 1 and the top seat 3, and the extrusion assembly 4 includes a processing barrel 41, a bracket 42, a die hole 43, a sleeve 44, a telescopic rod 45 and an extrusion seat 46, the bracket 42 is fixedly connected to the base 1, the processing barrel 41 is fixedly connected to the bracket 42, the die hole 43 is opened at the bottom of the processing barrel 41, and the sleeve 44 is fixedly connected to the top seat 3. The telescopic rod 45 is slidably connected to the inside of the sleeve 44, the extrusion seat 46 is fixedly connected to the telescopic rod 45, a driving assembly 5 is arranged on the top seat 3, and a cutting assembly 6 is arranged at the bottom of the processing barrel 41. The cutting assembly 6 includes a first gear 61, a slide rod 62, a cutting knife 63, a second spring 64, a wave ring 65, a limit rod 66, a semicircular plate 67, a grinding plate 68 and a third spring 69. The first gear 61 is rotatably connected to the processing barrel 41, and the slide rod 62 is slidably connected to the first gear 61. The two A cutting knife 63 is fixedly connected to the slide bar 62, two second springs 64 are respectively fixedly connected between the two ends of the slide bar 62 and the first gear 61, a wave ring 65 is fixedly connected to the bracket 42, a limit rod 66 is fixedly connected to the slide bar 62, and the limit rod 66 is slidably connected to the inner wall of the wave ring 65, two semicircular plates 67 are respectively fixedly connected to the bottom of the processing barrel 41 and the bracket 42, two grinding plates 68 are respectively slidably connected to the inside of the two semicircular plates 67, and two third springs 69 are respectively Fixedly connected between the inner walls of the two semicircular plates 67 and the two grinding plates 68, a driving assembly 5 is arranged on the top seat 3, the driving assembly 5 includes a hydraulic press 51, the hydraulic press 51 is fixedly connected to the top seat 3, a cooperative assembly 7 is arranged on the processing barrel 41, the cooperative assembly 7 includes a rotating column 75 and a second gear 76, the rotating column 75 is rotatably connected to the base 1, the second gear 76 is fixedly connected to the rotating column 75, the second gear 76 is meshed with the first gear 61, and the hydraulic press 51 cooperates with the second gear 76.

[0031] The inner wall of the processing barrel 41 is provided with a heating mechanism, which can heat the aluminum alloy ingot placed therein by supplying electricity, and the extrusion seat 46 can be placed exactly in the processing barrel 41 to extrude the softened aluminum alloy raw material. A mold is provided at the bottom of the processing barrel 41, and the mold is connected to the mold hole 43. The inner wall of the wave ring 65 is wavy, so when the limit rod 66 rotates with the first gear 61, the limit rod 66 will cause the sliding rod 62 and the cutting knife 63 to shake back and forth due to the resistance against the wave ring 65.

[0032] Further, such as Figure 2 and Figure 5 As shown, the driving assembly 5 further includes a lifting column 52 and a fixing plate 53. The lifting column 52 is fixedly connected to the piston rod of the hydraulic press 51. A plurality of fixing plates 53 are fixedly connected to the lifting column 52. The plurality of fixing plates 53 are distributed in a linear array.

[0033] Further, such as Figure 6 As shown, the driving assembly 5 also includes a connecting seat 54, a sliding seat 55 and a first pawl 56. The connecting seat 54 is fixedly connected to the extrusion seat 46, the sliding seat 55 is slidably connected to the inside of the connecting seat 54, the first pawl 56 is fixedly connected to the sliding seat 55, the first pawl 56 extends outside the connecting seat 54, and the first pawl 56 is meshed with the fixed plate 53. The actual shape of the fixed plate 53 matches the first pawl 56. When the fixed plate 53 moves downward, the first pawl 56 will be dragged downward, and when the fixed plate 53 moves upward, the first pawl 56 will not move upward.

[0034] Further, such as Figure 6 As shown, the driving assembly 5 also includes a pull rod 57 and a first spring 58. The pull rod 57 is fixedly connected to the sliding seat 55, and the pull rod 57 extends outside the connecting seat 54. The first spring 58 is fixedly connected between the sliding seat 55 and the inner wall of the connecting seat 54. When the fixed plate 53 moves downward, it can drive the first pawl 56 to move downward, thereby causing the extrusion seat 46 to move downward, but the extrusion seat 46 cannot be raised and reset. Therefore, when the extrusion seat 46 needs to be lifted, the pull rod 57 can be held and pulled to drive the sliding seat 55 and the first pawl 56 to move, so that the first pawl 56 can be disengaged from the gap of the fixed plate 53. At this time, the extrusion seat 46 can be lifted upward.

[0035] Further, such as Figure 7 As shown, the cooperative component 7 also includes a cylinder 71 and a support ring 72 . The support ring 72 is fixedly connected to the processing barrel 41 , and the cylinder 71 is rotatably connected to the support ring 72 .

[0036] Further, such as Figure 7 and Figure 8 As shown, the cooperative component 7 also includes a ball head rod 73 and a threaded groove 74. The ball head rod 73 is fixedly connected to the lifting column 52. The threaded groove 74 is opened on the inner wall of the cylinder 71. The ball head rod 73 is slidably connected to the inside of the threaded groove 74. When the lifting column 52 moves up and down, the ball head rod 73 at the bottom end thereof will also move up and down. Since the ball head rod 73 slides in the threaded groove 74, and the cylinder 71 is rotatably connected to the support ring 72, when the ball head rod 73 moves up and down, the cylinder 71 will also rotate accordingly.

[0037] Further, such as Figure 7As shown, the cooperative component 7 also includes a ratchet 77 and a second pawl 78. The ratchet 77 is fixedly connected to the rotating column 75. The second pawl 78 is arranged on the inner wall of the cylinder 71. The second pawl 78 is meshed with the ratchet 77. When the ball head rod 73 moves downward with the lifting column 52, the cylinder 71 and the second pawl 78 at its bottom rotate, but at this time the second pawl 78 will not drive the ratchet 77 to rotate. At this time, the aluminum alloy profile is being extruded from the die hole 43, and when the lifting column 52 drives the ball head rod 73 to move upward, the cylinder 71 rotates in the opposite direction. At this time, the second pawl 78 will drive the ratchet 77 to rotate, and the rotation of the ratchet 77 will drive the rotating column 75 and the second gear 76 thereon to rotate.

[0038] The specific working method is: first, the aluminum alloy ingot used for processing the aluminum alloy profile is thrown into the processing barrel 41. The barrel wall of the processing barrel 41 is provided with a heating mechanism, which can heat the aluminum alloy ingot, and then the hydraulic press 51 is started. After the hydraulic press 51 is started, its piston rod will reciprocate up and down, thereby driving the lifting column 52 to move up and down. During the up and down movement of the lifting column 52, the fixed plate 53 thereon will drive the first pawl 56 to move downward intermittently, and the downward movement of the first pawl 56 will drive the extrusion seat 46 to move downward until the extrusion seat 46 enters the processing barrel 41 and resists the aluminum alloy ingot. Then the extrusion seat 46 continues to move downward intermittently, and each time it moves downward, the aluminum alloy ingot will be squeezed downward for a section, and the extruded aluminum alloy ingot will pass through the die hole 43 to form an aluminum alloy profile. Since the extrusion seat 46 moves downward intermittently, the aluminum alloy profile will be extruded from the die hole 43 for a section, and then it will be stationary for a period of time, and then the next section of the aluminum alloy profile will be extruded again.

[0039] When the lifting column 52 moves up and down, the ball head rod 73 at its bottom end will also move up and down. Since the ball head rod 73 slides in the threaded groove 74 and the cylinder 71 is rotatably connected to the support ring 72, when the ball head rod 73 moves up and down, the cylinder 71 will also rotate accordingly. When the ball head rod 73 moves downward with the lifting column 52, the cylinder 71 and the second pawl 78 at its bottom rotate, but at this time the second pawl 78 will not drive the ratchet 77 to rotate. At this time, the aluminum alloy profile is being extruded from the die hole 43, and when the lifting column 52 drives the ball head rod 73 to move upward, the cylinder 71 rotates in the opposite direction. At this time, the second pawl 78 will drive the ratchet 77 to rotate, and the rotation of the ratchet 77 will drive the rotating column 75 and the second gear 76 thereon to rotate.

[0040] When the second gear 76 rotates, it drives the first gear 61 to rotate, and the first gear 61 rotates half a circle each time. During the half-circle rotation of the first gear 61, the slide bar 62 thereon rotates accordingly. Since the wave ring 65 is in a fixed state, when the slide bar 62 and the first gear 61 rotate, the limit rod 66 on the slide bar 62 also moves back and forth due to the inner wall of the wave ring 65. Therefore, the cutting knife 63 on the slide bar 62 rotates to cut the aluminum alloy profile below the die hole 43. While cutting, the cutting knife 63 moves back and forth with the slide bar 62. The first gear 61 rotates along with the second gear 61, and the second gear 61 rotates half a circle each time. Therefore, the two cutting knives 63 perform cutting work alternately. One cutting knife 63 is responsible for cutting at a time, and the other one can pass through two grinding plates 68 for cooling and grinding. The two cutting knives 63 perform cutting, cooling and grinding alternately, so that the cutting work can be carried out continuously, which greatly reduces the need for frequent knife changes during the cutting process.

[0041] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical solutions composed of equivalent replacement of the above technical features. Matters not covered in the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An extrusion device for aluminum alloy processing, comprising a base (1), a support (2) fixedly connected to the base (1), a top seat (3) fixedly connected to the support (2), characterized in that: An extrusion assembly (4) is provided on the base (1) and the top seat (3), and the extrusion assembly (4) comprises a processing barrel (41), a bracket (42), a die hole (43), a sleeve (44), a telescopic rod (45) and an extrusion seat (46), wherein the bracket (42) is fixedly connected to the base (1), the processing barrel (41) is fixedly connected to the bracket (42), the die hole (43) is opened at the bottom of the processing barrel (41), the sleeve (44) is fixedly connected to the top seat (3), the telescopic rod (45) is slidably connected to the inside of the sleeve (44), and the extrusion seat (46) is fixedly connected to the telescopic rod (45). The processing barrel (41) is provided with a cutting assembly (6), the cutting assembly (6) comprising a first gear (61), a sliding rod (62), a cutting knife (63), a second spring (64), a wave ring (65), a limit rod (66), a semicircular plate (67), a grinding plate (68) and a third spring (69), the first gear (61) is rotatably connected to the processing barrel (41), the sliding rod (62) is slidably connected to the first gear (61), the two cutting knives (63) are fixedly connected to the sliding rod (62), and the two The second springs (64) are respectively fixedly connected between the two ends of the slide bar (62) and the first gear (61); the wave ring (65) is fixedly connected to the bracket (42); the limit rod (66) is fixedly connected to the slide bar (62); the limit rod (66) is slidably connected to the inner wall of the wave ring (65); the two semicircular plates (67) are respectively fixedly connected to the bottom of the processing barrel (41) and the bracket (42); the two grinding plates (68) are respectively slidably connected to the inside of the two semicircular plates (67); and the two third springs (69) are respectively fixedly connected to the inner walls of the two semicircular plates (67). and two grinding plates (68), a driving assembly (5) is arranged on the top seat (3), the driving assembly (5) includes a hydraulic press (51), the hydraulic press (51) is fixedly connected to the top seat (3), a cooperative assembly (7) is arranged on the processing barrel (41), the cooperative assembly (7) includes a rotating column (75) and a second gear (76), the rotating column (75) is rotatably connected to the base (1), the second gear (76) is fixedly connected to the rotating column (75), the second gear (76) is meshed with the first gear (61), and the hydraulic press (51) cooperates with the second gear (76).

2. The extrusion device for aluminum alloy processing according to claim 1, characterized in that: The driving assembly (5) further comprises a lifting column (52) and a fixing plate (53), wherein the lifting column (52) is fixedly connected to a piston rod of a hydraulic press (51), and a plurality of fixing plates (53) are fixedly connected to the lifting column (52), and the plurality of fixing plates (53) are distributed in a linear array.

3. The extrusion device for aluminum alloy processing according to claim 2, characterized in that: The driving assembly (5) further comprises a connecting seat (54), a sliding seat (55) and a first pawl (56); the connecting seat (54) is fixedly connected to the extrusion seat (46); the sliding seat (55) is slidably connected to the interior of the connecting seat (54); the first pawl (56) is fixedly connected to the sliding seat (55); the first pawl (56) extends out of the connecting seat (54); and the first pawl (56) is meshed with the fixing plate (53).

4. The extrusion device for aluminum alloy processing according to claim 3, characterized in that: The driving assembly (5) further comprises a pull rod (57) and a first spring (58), wherein the pull rod (57) is fixedly connected to the sliding seat (55), the pull rod (57) extends outside the connecting seat (54), and the first spring (58) is fixedly connected between the inner wall of the sliding seat (55) and the connecting seat (54).

5. The extrusion device for aluminum alloy processing according to claim 1, characterized in that: The cooperative component (7) further comprises a cylinder (71) and a support ring (72), wherein the support ring (72) is fixedly connected to the processing barrel (41), and the cylinder (71) is rotatably connected to the support ring (72).

6. The extrusion device for aluminum alloy processing according to claim 5, characterized in that: The cooperative component (7) further comprises a ball head rod (73) and a threaded groove (74); the ball head rod (73) is fixedly connected to the lifting column (52); the threaded groove (74) is formed on the inner wall of the cylinder (71); and the ball head rod (73) is slidably connected to the inside of the threaded groove (74).

7. The extrusion device for aluminum alloy processing according to claim 6, characterized in that: The cooperative component (7) further comprises a ratchet (77) and a second ratchet pawl (78), wherein the ratchet (77) is fixedly connected to the rotating column (75), and the second ratchet pawl (78) is arranged on the inner wall of the cylinder (71), and the second ratchet pawl (78) is meshed with the ratchet (77).

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