A cooling device for a blown film machine

Abstract

This application discloses a cooling device for a blown film machine, relating to the field of film production auxiliary technology. It includes a support frame with a non-contact adjustable mechanism on its side wall. The application utilizes a motor to drive a gear ring to rotate, thereby rotating a cylinder and introducing external airflow into the inner wall of the cylinder. The gear ring also drives a rotating rod to rotate, preventing the cleaning cylinder from being blocked. Inclined blades then drive the external airflow to generate a spiral airflow, cooling the plastic film without contact with it. This avoids the transmission of equipment vibration to the plastic film surface. Compared to side-to-side cooling, using rotation to drive airflow ensures a consistent temperature difference around the plastic film, preventing cooling dead zones.

Description

Technical Field

[0001] This application relates to the field of auxiliary technology for thin film production, and in particular to a cooling device for a blown film machine. Background Technology

[0002] Film blowing machines are key equipment in the plastics processing industry for the continuous production of plastic films. They utilize the process principle of extrusion blow molding to melt and plasticize plastic particles and extrude them into tubular preforms. Then, they are blown into film bubbles by internal air, cooled and shaped, and then rolled into cylindrical films or cut into flat films.

[0003] For example, CN222807593U describes a film cooling and forming device for a blown film machine. By moving the cooling roller, the second rotating block moves, and in conjunction with the spring, the first rotating block moves, so that the air outlet pipe always fits against the two side walls of the film.

[0004] The aforementioned device, which uses a combination of cooling rollers and springs, generates vibrations transmitted from the equipment during cooling, resulting in resonance and affecting the surface finish of the plastic film. Additionally, the cooling process on both sides can cause heat to concentrate at the edges of the plastic film, preventing the heat from being reduced in time and thus affecting the cooling effect. Utility Model Content

[0005] To improve the problems of poor cooling effect and unstable product quality, this application provides a cooling device for blown film machines.

[0006] The cooling device for a blown film machine provided in this application adopts the following technical solution: A cooling device for a blown film machine includes a support frame, wherein a non-contact adjustable mechanism is provided on the side wall of the support frame. The contactless adjustable mechanism includes a cylinder disposed on the side wall of the support, a drive assembly for driving the cylinder to rotate is disposed at the top of the cylinder, a cleaning cylinder is disposed on the outer wall of the cylinder, a plastic film is disposed through the middle of the inner cavity of the cylinder, a plurality of fan blades for cooling the plastic film are disposed on the inner wall of the cylinder, and an adjustment assembly for adjusting the angle of the fan blades is disposed at the top of the cylinder.

[0007] By adopting the above technical solution, the cylinder is driven to rotate by the gear, thereby driving the airflow through the cylinder, thus cooling the plastic film without contact. The fan blades are driven to rotate by the adjustment plate, thereby adjusting the ability of the fan blades to drive the airflow when rotating.

[0008] Preferably, the contactless adjustable mechanism further includes a limiting plate fixedly connected to the side wall of the bracket, the side wall of the bracket is fixedly connected to a fixing plate, the driving component includes a motor, a gear one, a gear ring, and a gear two, the top of the fixing plate is fixedly connected to the bottom of the motor, and the output shaft end of the motor movably passes through the top of the fixing plate.

[0009] By adopting the above technical solution, the fixing plate serves as the mounting base for the motor, ensuring a reliable connection between it and the side wall of the bracket, providing stable support for subsequent transmission. The design of the motor output shaft passing through the top of the fixing plate not only ensures that the shaft end can effectively transmit power, but also provides the necessary radial support points through the fixing plate, ensuring the concentricity and smoothness of the initial rotation of the transmission shaft.

[0010] Preferably, a baffle is rotatably connected to the side wall of the bracket, the motor output shaft end is fixedly connected to the middle of gear one, one side wall of the gear is meshed with a gear ring, the side wall of the gear ring is meshed with gear two, and a rotating rod one is fixedly connected to the top of gear two.

[0011] By adopting the above technical solution, the motor directly drives gear one, gear one meshes with the gear ring to achieve initial deceleration and torque increase, the gear ring then meshes with gear two, gear two drives the vertical shaft rotating rod one to rotate, thereby making the rotational transmission more stable and limiting the pair of cylinders through the limiting plate.

[0012] Preferably, a second limiting plate is fixedly connected to one side wall of the limiting plate and is rotatably connected to the first rotating rod. The outer wall of the first rotating rod is fixedly connected through the cleaning cylinder. A first connecting ring is fixedly connected to the bottom of the gear ring and fits against the inner wall of the first limiting plate. A first limiting ring is fixedly connected to the outer wall of the first connecting ring and is rotatably connected to the first limiting plate.

[0013] By adopting the above technical solution, the limiting plate 2 serves as a bearing seat, supporting the upper end of the rotating rod 1. Together with the fixing plate, it ensures the stability and coaxiality of the rotation of the rotating rod 1. The cleaning cylinder is directly fixed on the rotating rod 1 and rotates with it, using its flexibility to gently wipe the surface of the cylinder to remove dust or assist in cooling.

[0014] Preferably, the bottom of the limiting ring one is fixedly connected to the top of the cylinder, the bottom of the cylinder is fixedly connected to the limiting ring two, the side wall of the limiting ring two is rotatably connected to the limiting plate three which is fixedly connected to the side wall of the bracket, the inner wall of the limiting ring two is fixedly connected to the connecting ring two, and the inner wall of the connecting ring two is fixedly connected to the limiting plate four.

[0015] By adopting the above technical solution, the cylinder, as the core component, is driven to rotate by the first limiting ring, and the cylinder drives the second limiting ring fixed to it.

[0016] Preferably, the adjustment assembly includes a second rotating rod, a horizontal ring, a vertical ring, and an adjustment plate. The outer wall of the third limiting plate is fixedly connected to a horizontal plate that is rotatably connected to the first rotating rod. The inner wall of the first connecting ring is fixedly connected to an inner connecting plate. The top of the inner connecting plate movably passes through the second rotating rod. The outer wall of the second rotating rod is fixedly connected to the fan blade.

[0017] By adopting the above technical solution, the horizontal plate is fixed on the limiting plate three as another bearing component, providing an additional support point for the lower end of the rotating rod one, further enhancing the rotational stability of the rotating rod one. The inner plate is fixed on the inner wall of the rotating connecting ring one, serving as the mounting base for the internal component fan blade.

[0018] Preferably, a first collar is fixedly passed through the outer wall of the second rotating rod, a telescopic rod is fixedly connected to one side wall of the collar, a second collar is fixedly connected to the end of the telescopic rod away from the first collar, and the bottom of the second collar is rotatably connected to the horizontal ring.

[0019] By adopting the above technical solution, the first collar is fixed to the second rotating rod as a connecting component, one end of the telescopic rod is fixed to one side wall of the collar, and the other end is fixed to the second collar. The second collar serves as an adjusting component, and its bottom is rotatably connected to the horizontal ring, thereby making the structural movement more stable.

[0020] Preferably, the top of the horizontal ring is fixedly connected to the vertical ring, the outer wall of the vertical ring is fixedly connected to the end of the adjusting plate near the vertical ring, the top of the adjusting plate is threaded with a rotating nut that is threadedly connected to the gear ring, and the top of the gear ring is provided with a positioning hole.

[0021] By adopting the above technical solution, the vertical ring is fixed on the top of the horizontal ring, the adjusting plate is easy to rotate manually, and the rotating nut passes through the hole at the top of the adjusting plate, which makes installation easier.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. The motor drives the gear ring to rotate, which in turn drives the cylinder to rotate, thereby introducing external airflow into the inner wall of the cylinder. The gear ring also drives the rotating rod to rotate, which in turn drives the cleaning cylinder to rotate, preventing the holes on the outer wall of the cylinder from being blocked. The tilting blades drive the external airflow to generate a spiral airflow, which cools the plastic film without contact with it. This avoids the vibration of the equipment being transmitted to the surface of the plastic film. Compared with the side-to-side contact cooling, the rotation-driven airflow ensures that the temperature difference around the plastic film is consistent, avoiding the formation of cooling dead zones. 2. The vertical ring rotates with the help of the adjusting plate, which in turn rotates the horizontal ring, which in turn rotates the first collar ring. The first collar ring rotates the fan blades, thereby adjusting the tilt angle of the fan blades. When the fan blade tilt angle is small, the airflow can vertically impact the membrane bubble, thus achieving high-speed rapid cooling and inhibiting crystallization. When the fan blade tilt angle is large, the airflow forms a spiral wrap, thus achieving uniform and slow cooling. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the overall structure of this application; Figure 2 This is a partial schematic diagram of the motor in this application; Figure 3 This is a partial schematic diagram of the cleaning cylinder in this application; Figure 4 This is a partial schematic diagram of the rotating nut in this application; Figure 5 This is a schematic diagram of the cross-section of the limiting plate in this application; Figure 6 This is a partial schematic diagram of two limiting rings in this application.

[0024] Figure label: 1. Bracket; 2. Non-contact adjustable mechanism; 21. Limiting plate one; 22. Fixing plate; 23. Motor; 24. Baffle; 25. Gear one; 26. Gear ring; 27. Gear two; 28. Rotating rod one; 29. ​​Limiting plate two; 210. Cleaning cylinder; 211. Connecting ring one; 212. Limiting ring one; 213. Cylinder; 214. Limiting ring two; 215. Limiting plate three; 216. Connecting ring two; 217. Limiting plate four; 218. Horizontal plate; 219. Inner plate; 220. Rotating rod two; 221. Fan blade; 222. Collar one; 223. Telescopic rod; 224. Collar two; 225. Horizontal ring; 226. Vertical ring; 227. Adjusting plate; 228. Rotating nut; 229. Positioning hole; 3. Film blowing equipment; 4. Plastic film; 5. Winding equipment. Detailed Implementation

[0025] The following is in conjunction with the appendix Figures 1-6 This application will be described in further detail.

[0026] This application discloses a cooling device for a blown film machine.

[0027] Reference Figures 1-4A cooling device for a blown film machine includes a support 1. A non-contact adjustable mechanism 2 is provided on the side wall of the support 1. The non-contact adjustable mechanism 2 also includes a limiting plate 21 fixedly connected to the side wall of the support 1, which remains horizontal. A fixing plate 22 is fixedly connected to the side wall of the support 1. The bottom of a motor 23 is fixedly connected to the top of the fixing plate 22. The motor 23 is a DC type, with a voltage controlled at 12V and a power setting of 60W, thus providing a stable rotation speed. A circular hole is provided through the top of the fixing plate 22. The output shaft end of motor 23 is movably connected through the circular hole 1, thereby allowing the output shaft end of motor 23 to be rotatably connected to the fixed plate 22. A support is fixedly connected to the side wall of bracket 1, and the support is rotatably connected to the baffle 24. The baffle 24 is L-shaped. By rotating the baffles 24 on both sides, the cylinder 213 will be closed, thereby preventing the surrounding airflow from interfering with the cylinder 213. The output shaft end of motor 23 is fixedly connected through the middle of gear 25. The center of gear 25 overlaps with the center of the output shaft end of motor 23. The teeth on the side wall of gear 25 mesh with the teeth on the side wall of gear ring 26.

[0028] The staff first rotates the baffles 24 on both sides to close them. Then the blown film equipment 3 starts to blow out the plastic film 4. The plastic film 4 will pass through the inner wall of the cylinder 213 and then be wound up by the winding equipment 5. Then, during the process of the plastic film 4 being transported from the support 1 to the plastic film 4, the motor 23 will drive the gear 1 25 to rotate. The rotation of the gear 1 25 will drive the gear ring 26 to rotate, and the gear ring 26 will drive the gear 2 27 to rotate.

[0029] Reference Figures 2-4 Gear 25 is aligned with gear ring 26 at both top and bottom. The teeth on the sidewall of gear ring 26 mesh with the teeth on the sidewall of gear 27. The top of gear 27 is fixedly connected to rotating rod 28, which remains vertical. The sidewall of limiting plate 21 is fixedly connected to limiting plate 29. A second circular hole is provided at the top of limiting plate 29, which is rotatably connected to rotating rod 28, thus allowing limiting plate 29 to rotatably connect with rotating rod 28. All toothed components are made of aluminum alloy or steel alloy with a hardness requirement of HRC 50 to ensure wear resistance and long-term stable operation. A third circular hole is vertically provided at the top of cleaning cylinder 210, which is fixedly connected to the outer wall of rotating rod 28. The outer diameter of cleaning cylinder 210 is 60mm and its length is 150mm, suitable for cleaning the outer wall of cylinder 213. Cleaning cylinder 210 is made of high-density sponge with a density of 300kg / m³. 3 It is flexible and can effectively remove dust and impurities adhering to the outer wall of the cylinder 213. Its main purpose is to squeeze and clear the holes on the side wall of the cylinder 213 to prevent air from being blocked when it is introduced into the cylinder 213.

[0030] Subsequently, gear 27 will drive rotating rod 28 to rotate, rotating rod 28 will drive cleaning cylinder 210 to rotate, gear ring 26 will also drive connecting ring 211 to rotate, connecting ring 211 will drive limiting ring 212 to rotate, limiting ring 212 will drive cylinder 213 to rotate, and cylinder 213 will drive limiting ring 214 to rotate.

[0031] Reference Figures 2-3 The main function of the cleaning cylinder 210 is to prevent the holes on the side wall of the cylinder 213 from becoming clogged. Even after prolonged use and when the sponge becomes contaminated with dust, it can still effectively unclog the holes on the side wall of the cylinder 213. The bottom of the toothed ring 26 is fixedly connected to the top of the connecting ring 211. The inner diameter of the toothed ring 26 is consistent with the inner diameter of the connecting ring 211. The inner diameter of the limiting plate 21 is consistent with the outer wall of the connecting ring 211, thereby ensuring that the connecting ring 211 fits snugly against the inner wall of the limiting plate 21. The outer wall of connecting ring 211 is consistent with the inner diameter of limiting ring 212, thereby fixing connecting ring 211 and limiting ring 212. The bottom of limiting plate 21 is provided with a rotating groove, which is rotatably connected to limiting plate 21, thereby fixing limiting ring 212 to limiting plate 21. The bottom of limiting ring 212 is fixedly connected to the top of cylinder 213, and the bottom of cylinder 213 is fixedly connected to the top of limiting ring 214. The inner diameter of cylinder 213 is consistent with the outer diameter of limiting ring 214.

[0032] Subsequently, the second limiting ring 214 will drive the second connecting ring 216 to rotate, the second connecting ring 216 will drive the fourth limiting plate 217 to rotate, and the first connecting ring 211 will drive the inner plate 219 to rotate, thereby driving the airflow inside the cylinder 213. At the same time, the inner plate 219 will also drive the fan blade 221 to rotate.

[0033] Reference Figures 4-6The top of the limiting plate 3 215 has a rotating groove 2. The side wall of the limiting ring 2 214 is rotatably connected to the rotating groove 2, thereby making the limiting ring 2 214 rotatably connected to the limiting plate 3 215. The side of the limiting plate 3 215 near the bracket 1 is fixedly connected to the side wall of the bracket 1. The limiting plate 3 215 is kept in a horizontal state. The inner diameter of the limiting ring 2 214 is consistent with the outer diameter of the connecting ring 2 216, thereby making the connecting ring 2 216 fixedly connected to the limiting ring 2 214. The inner wall of the connecting ring 2 216 is fixedly connected to the end of the limiting plate 4 217 near the connecting ring 2 216. The outer wall of the limiting plate 3 215 is fixedly connected to the end of the horizontal plate 218 near the limiting plate 3 215. The top of the horizontal plate 218 has a through hole 4, which is rotatably connected to the rotating rod 1 28, thereby making the horizontal plate 218 rotatably connected to the rotating rod 1 28. The inner wall of the connecting ring 1 211 is fixedly connected to the end of the inner plate 219 near the connecting ring 1 211. The top of the inner plate 219 has a through hole 5, which is rotatably connected to the rotating rod 220, thereby making the rotating rod 220 rotatably connected to the inner plate 219.

[0034] When the angle of the fan blade 221 needs to be adjusted, the operator first rotates the rotating nut 228 to release the thread lock between the rotating nut 228 and the gear ring 26, and then the operator rotates the adjusting plate 227.

[0035] Reference Figure 4 The outer wall of the rotating rod 220 is fixedly connected to one end of the fan blade 221. The fan blade 221 has a length of 150mm, a width of 100mm, and a thickness of 5mm. The fan blade 221 is made of aluminum alloy or high-strength plastic. The angle adjustment range of the fan blade 221 is 0-30 degrees. The outer wall of the rotating rod 220 is rotatably connected to the top of the limiting plate 4 217. Multiple fan blades 221 are symmetrically located inside the cylinder 213. The outer wall of the rotating rod 220 is fixedly connected to the inner wall of the collar 222. The side of the collar 222... The wall is fixedly connected to the fixed end of the telescopic rod 223. The telescopic end of the telescopic rod 223 away from the first collar 222 is fixedly connected to the side wall of the second collar 224. The middle of the second collar 224 is rotatably connected to a rotating shaft. The bottom of the rotating shaft is fixedly connected to the top of the horizontal ring 225, so that the second collar 224 is rotatably connected to the horizontal ring 225. The top of the horizontal ring 225 is fixedly connected to the bottom of the vertical ring 226. The outer wall of the vertical ring 226 is in contact with the outer wall of the horizontal ring 225. The outer wall of the vertical ring 226 is in contact with the inner wall of the toothed ring 26.

[0036] Subsequently, the adjusting plate 227 will drive the vertical ring 226 to rotate, the vertical ring 226 will drive the horizontal ring 225 to rotate, the horizontal ring 225 will drive the first ring 222 to rotate through the second ring 224, and the first ring 222 will drive the fan blade 221 to rotate, thereby adjusting the tilt angle of the fan blade 221.

[0037] Reference Figures 4-6The outer wall of the vertical ring 226 is fixedly connected to the adjusting plate 227. The top of the adjusting plate 227 has a threaded through hole, and the rotating nut 228 is threaded through the threaded through hole, so that the rotating nut 228 is threadedly connected to the adjusting plate 227. The top of the gear ring 26 has a threaded through hole, and the positioning hole 229 is opened on the top of the gear ring 26. The rotating nut 228 and the positioning hole 229 are threadedly matched. The blown film device 3 is installed at the bottom of the bracket 1. The plastic film 4 is blown out through the top of the blown film device 3 and then pressed into a flat film. Then the plastic film 4 is conveyed to the winding device 5 through the rollers on the side wall of the bracket 1 for winding. The rotating nut 228 adopts an M8 thread and is made of stainless steel, which has the characteristics of high temperature resistance and corrosion resistance.

[0038] By rotating the rotary nut 228, the positioning hole 229 is threadedly connected, thereby fixing the adjusting plate 227.

[0039] The implementation principle of a cooling device for a blown film machine according to an embodiment of this application is as follows: The operator first closes the baffles 24 on both sides, then the film blowing equipment 3 begins to blow out the plastic film 4. The plastic film 4 passes through the inner wall of the cylinder 213 and is then wound up by the winding equipment 5. During the process of the plastic film 4 being conveyed from the support 1, the motor 23 drives the gear 25 to rotate. The rotation of the gear 25 drives the inner plate 219 to rotate, thereby driving the airflow inside the cylinder 213. The rotation of the cylinder 213 introduces external air into the cylinder 213. At the same time, the inner plate 219 also drives the fan blades 221 to rotate. When the fan blades 221 rotate, they further drive the internal airflow to form a spiral shape, thereby cooling the plastic film 4. This cooling process is achieved without direct contact with the plastic film 4, and the airflow does not blow directly onto the surface of the plastic film 4. The spiral airflow also avoids cooling dead corners or other areas of the plastic film 4. When uneven heat distribution occurs, and the angle of the fan blade 221 needs to be adjusted, the operator rotates the adjustment plate 227. The adjustment plate 227 drives the vertical ring 226 to rotate, which in turn drives the horizontal ring 225 to rotate. The horizontal ring 225 then drives the first ring 222 to rotate via the second ring 224. The first ring 222 drives the fan blade 221 to rotate, thereby adjusting the tilt angle of the fan blade 221. When the angle of the fan blade 221 is small, the airflow speed is fast, which shortens the cooling time of the plastic film 4 and produces a rapid cooling effect. When the angle of the fan blade 221 is large, the airflow will circulate around the plastic film 4 for cooling, resulting in slow and uniform cooling. This ensures that the plastic film 4 reaches the required cooling state when it leaves the bottom of the cylinder 213. The adjustment plate 227 is then fixed by rotating the rotating nut 228 to connect the positioning hole 229 with a thread.

[0040] The above are merely optional embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A cooling device for a blown film machine, characterized in that: Includes a bracket (1), and the side wall of the bracket (1) is provided with a non-contact adjustable mechanism (2); The non-contact adjustable mechanism (2) includes a cylinder (213) disposed on the side wall of the support (1). A drive assembly for driving the cylinder (213) to rotate is disposed on the top of the cylinder (213). A cleaning cylinder (210) is disposed on the outer wall of the cylinder (213). A plastic film (4) is disposed through the middle of the inner cavity of the cylinder (213). A plurality of fan blades (221) for cooling the plastic film (4) are disposed on the inner wall of the cylinder (213). An adjustment assembly for adjusting the angle of the fan blades (221) is disposed on the top of the cylinder (213).

2. The cooling device for a blown film machine according to claim 1, characterized in that: The non-contact adjustable mechanism (2) also includes a limiting plate (21) fixedly connected to the side wall of the bracket (1). The drive assembly includes a motor (23), a gear (25), a gear ring (26), and a gear (27). A fixing plate (22) is fixedly connected to the side wall of the bracket (1). The top of the fixing plate (22) is fixedly connected to the bottom of the motor (23). The output shaft of the motor (23) moves through the top of the fixing plate (22).

3. A cooling device for a blown film machine according to claim 2, characterized in that: The bracket (1) has a baffle (24) rotatably connected to its side wall. The output shaft of the motor (23) is fixedly connected to the middle of the gear one (25). The side wall of the gear one (25) is meshed with the gear ring (26). The side wall of the gear ring (26) is meshed with the gear two (27). The top of the gear two (27) is fixedly connected with a rotating rod one (28).

4. A cooling device for a blown film machine according to claim 3, characterized in that: The side wall of the first limiting plate (21) is fixedly connected to the second limiting plate (29) which is rotatably connected to the first rotating rod (28). The outer wall of the first rotating rod (28) is fixedly connected to the cleaning cylinder (210). The bottom of the toothed ring (26) is fixedly connected to the first connecting ring (211) which fits against the inner wall of the first limiting plate (21). The outer wall of the first connecting ring (211) is fixedly connected to the first limiting ring (212) which is rotatably connected to the first limiting plate (21).

5. A cooling device for a blown film machine according to claim 4, characterized in that: The bottom of the limiting ring one (212) is fixedly connected to the top of the cylinder (213), the bottom of the cylinder (213) is fixedly connected to the limiting ring two (214), the side wall of the limiting ring two (214) is rotatably connected to the limiting plate three (215) which is fixedly connected to the side wall of the bracket (1), the inner wall of the limiting ring two (214) is fixedly connected to the connecting ring two (216), and the inner wall of the connecting ring two (216) is fixedly connected to the limiting plate four (217).

6. A cooling device for a blown film machine according to claim 5, characterized in that: The adjustment assembly includes a second rotating rod (220), a horizontal ring (225), a vertical ring (226), and an adjustment plate (227). The outer wall of the third limiting plate (215) is fixedly connected to a horizontal plate (218) that is rotatably connected to the first rotating rod (28). The inner wall of the first connecting ring (211) is fixedly connected to an inner connecting plate (219). The top of the inner connecting plate (219) is movably connected to the second rotating rod (220). The outer wall of the second rotating rod (220) is fixedly connected to the fan blade (221).

7. A cooling device for a blown film machine according to claim 6, characterized in that: The outer wall of the rotating rod 2 (220) is fixedly penetrated by a collar 1 (222), and a telescopic rod (223) is fixedly connected to the side wall of the collar 1 (222). The end of the telescopic rod (223) away from the collar 1 (222) is fixedly connected to a collar 2 (224), and the bottom of the collar 2 (224) is rotatably connected to the horizontal ring (225).

8. A cooling device for a blown film machine according to claim 7, characterized in that: The top of the horizontal ring (225) is fixedly connected to the vertical ring (226), and the outer wall of the vertical ring (226) is fixedly connected to the end of the adjusting plate (227) near the vertical ring (226). The top of the adjusting plate (227) is threaded with a rotating nut (228) that is threadedly connected to the toothed ring (26). The top of the toothed ring (26) is provided with a positioning hole (229).

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