Automatic polishing device for circumference of piston ring

Abstract

An automatic grinding device for the circumference of a piston ring comprises a base, a first screw is rotationally arranged on the base, a sliding base is arranged on the first screw, a first motor is connected to one side of the base, the first screw is connected to the output of the first motor, a first support is connected to the sliding base, and a second support is connected to one end of the base. A plurality of placing positions for placing piston rings are arranged on the bracket II; a clamping assembly is connected to the first support. A plurality of piston rings can be clamped and taken at the same time through the clamping assembly, meanwhile, the clamping assembly can be controlled to rotate at a low speed, the outer ring faces of the clamped piston rings can be ground circle by circle, and the grinding effect is guaranteed; and dust generated by grinding can be collected by arranging a dust cover and an air nozzle, and dust leakage is avoided.

Description

Technical Field

[0001] This invention relates to the field of polishing, and more specifically to an automatic piston ring circumference polishing device. Background Technology

[0002] Piston rings are the "heart seals" of an engine. The quality of the machining of their circumferential surface directly determines the engine's sealing performance, fuel consumption, power output, and lifespan. Grinding, or finishing, is a crucial step in the manufacturing process. The fundamental purpose of the grinding process is to form an ideal micro-geometry on the circumferential surface of the piston ring to meet the following demanding working requirements.

[0003] Current piston ring grinding processes involve grinding each piston ring individually using a grinding device. While this method is convenient for operation in a closed environment and avoids dust, it is inefficient. However, simultaneously grinding multiple piston rings at multiple grinding stations presents challenges in automating the loading and unloading of multiple rings and ensuring the grinding stations remain enclosed during grinding. This invention provides an automatic circumferential grinding device for piston rings that allows for the simultaneous loading and unloading of multiple piston rings while maintaining a dust cover that is open during loading and unloading and closed during grinding. Summary of the Invention

[0004] In response to the problems raised in the background art, the present invention provides an automatic piston ring circumference grinding device to solve them, and the present invention will be further described below.

[0005] An automatic piston ring circumferential grinding device includes a base, a screw rotatably mounted on the base, a slide on the screw, a motor connected to one side of the base, the screw connected to the output of the motor, a bracket connected to the slide, and a second bracket connected to one end of the base, the second bracket having multiple placement positions for placing piston rings; a clamping assembly connected to the first bracket; the clamping assembly includes a rotating shaft rotatably mounted on the first bracket, a rotating cylinder connected to the end of the rotating shaft, a guide groove on the rotating cylinder, a coaxial main shaft inside the rotating shaft, a blade connected to the main shaft, a sliding groove on the blade, a sliding shaft and a lifting component within the sliding groove, the sliding shaft being connected to the lifting component. Above, the lifting component passes through the guide groove. One end of the lifting component exposed on the rotating drum is connected to a fixed chuck. The fixed chuck has a movable bottom clamp plate inside. A guide post passing through the fixed chuck is connected to the bottom clamp plate. A wing plate is connected to the guide post. A second sliding groove is provided on the wing plate. A sliding shaft is provided in the second sliding groove. Connecting plates are connected to both ends of the sliding shaft. The fixed chuck has a clearance groove. The connecting plate passes through the clearance groove and is connected to a side clamp plate. The fixed chuck has a spring placement groove. A spring is placed inside the spring placement groove. The spring is set outside the guide post. A stop ring is connected to the guide post. An electric push rod is connected to the bracket. One end of the main shaft extends to the outside of the rotating shaft. The output of the electric push rod is connected to the rotating shaft.

[0006] Preferably, a bracket is connected to the base, and a grinding roller is mounted on the bracket. A gearbox is also connected to the bracket, with its input connected to a second motor. The gearbox has two outputs: one connected to the grinding roller, and the other an exposed output gear. A gear is connected to the main shaft, meshing with the exposed output gear of the gearbox. When the second motor starts, its high-speed rotation drives the grinding roller to rotate at high speed, while its low-speed rotation drives the main shaft through the gear, causing the tightly clamped piston ring to rotate slowly in a circumferential direction.

[0007] Preferably, a second screw is rotatably connected to the base, and a third motor is fixed to the base. The second screw is connected to the output end of the third motor, and the bracket is fitted onto the second screw. The third motor can control the position of the bracket on the second screw, thereby controlling the contact state between the grinding roller and the piston ring. After grinding, when the clamping assembly releases the ground piston ring into the placement position, the grinding roller needs to disengage from the piston ring to prevent the laterally shifting piston ring from sliding against the grinding roller and causing scratches.

[0008] Preferably, a dust cover is attached to the base. During grinding, the dust cover can enclose the grinding roller and piston rings to prevent dust from flying. A groove is provided on one side of the dust cover for the gearbox to be installed, and a second clearance groove is provided along the axis of the main shaft for the bracket to slide.

[0009] Preferably, the dust cover is equipped with a nozzle at the bottom. The nozzle is designed to maintain a negative pressure inside the dust cover, so that the dust generated during grinding will be drawn out of the device by the airflow, thus preventing the dust from flying around.

[0010] Preferably, a side sealing plate is connected to the bracket. The side sealing plate moves together with the bracket and cooperates with the dust cover to ensure lateral sealing during grinding.

[0011] Preferably, the dust cover is also connected to a motor four, the output of which is connected to a gear one. A column shaft is connected to the outer wall of the dust cover, and a rotating cover is mounted on the column shaft. A gear two is connected to the rotating cover, and the gear two is fitted onto the column shaft. The gear two meshes with the gear one. A sealing strip is connected to the rotating cover. The rotating cover is designed to be driven to rotate and seal one side of the dust cover after the clamping component retracts into place. At the same time, the sealing strip also covers the clearance groove two, ensuring the dustproof effect.

[0012] Preferably, the inner wall of the dust cover is connected to a brush, which is designed to clean the polished surface in a timely manner.

[0013] Preferably, the dust cover has a groove, and a guide rod is connected to the outer wall. The guide rod runs horizontally across the groove, and a slider is connected to the brush. The slider is slidably mounted on the guide rod. A limit cap is connected to one end of the guide rod, and a spring is sleeved on the guide rod between the slider and the limit cap. The side wall of the dust cover has a groove, and a slider is provided at the groove. The slider is connected to the slider through a pull wire, and one end of the slider extends outside the dust cover and interacts with the rotating cover.

[0014] Beneficial effects: Compared with the prior art, in this invention, multiple piston rings can be clamped and removed at the same time by means of a clamping component. At the same time, the clamping component can be rotated slowly in a controlled manner, which can achieve grinding of the outer ring surface of the clamped piston rings one ring at a time, ensuring the grinding effect. By setting a dust cover and a vent, the dust generated during grinding can be collected to prevent dust leakage. The rotating cover on the side wall of the dust cover allows the piston rings to enter and exit when opened, and when closed, it can cover the entry and exit channel and the second clearance groove on the side of the dust cover to ensure the dust prevention effect. On the other hand, when opened, it can also trigger the brush to retract, so as to avoid the brush from obstructing the movement of the piston rings. After resetting, the brush is in close contact with the piston ring to be ground, ensuring cleaning and grinding effect. Attached Figure Description

[0015] Figure 1 : A schematic diagram of the structure of the present invention.

[0016] Figure 2 : Schematic diagram of the clamping assembly.

[0017] Figure 3 : Schematic diagram of the main shaft structure of the clamping assembly.

[0018] Figure 4 : Figure 3 Cross-sectional view of the structure at point A in the middle.

[0019] Figure 5 : A diagram showing the effect of the clamping assembly tightly clamping the piston ring.

[0020] Figure 6 : Schematic diagram of the grinding roller.

[0021] Figure 7 : Schematic diagram of the dust cover structure.

[0022] Figure 8 : Figure 7 Sectional view of the structure at point B.

[0023] Figure 9 : A schematic diagram of the structure of a brush.

[0024] Figure 10 : Figure 9 Cross-sectional view of the structure at point C.

[0025] In the diagram: 1. Base; 2. Screw 1; 3. Slide; 4. Motor 1; 5. Bracket 1; 6. Bracket 2; 7. Rotary shaft; 8. Rotary cylinder; 801. Guide groove; 9. Main shaft; 10. Blade; 101. Slide 1; 11. Lifting component; 12. Fixed chuck; 121. Alternating groove; 122. Spring placement groove; 13. Bottom clamp plate; 14. Guide column; 15. Wing plate; 151. Slide 2; 16. Connecting plate; 17. Side clamp plate; 18. Spring 1; 19. Stop ring; 20. Electric push rod; 21. Piston ring; 22. Placement position. 23. Bracket; 24. Grinding roller; 25. Gearbox; 26. Motor II; 27. Gear; 28. Screw II; 29. ​​Motor III; 30. Dust cover; 301. Alternating groove II; 302. Slide groove I; 303. Slide groove II; 31. Nozzle; 32. Side sealing plate; 33. Motor IV; 34. Gear I; 35. Column shaft; 36. Rotary cover; 37. Gear II; 38. Seal; 39. Brush; 40. Guide rod; 41. Sliding head; 42. Limit cap; 43. Spring II; 44. Cable clamp; 45. Slide rod; 46. Pull cable. Detailed Implementation

[0026] Next, we will combine the appendix Figure 1-10 A specific embodiment of the present invention will be described in detail below.

[0027] Reference Appendix Figure 1 An automatic piston ring circumferential grinding device includes a base 1, a screw 2 rotatably mounted on the base 1, a slide 3 mounted on the screw 2, and a motor 4 connected to one side of the base 1. The screw 2 is connected to the output of the motor 4, and the motor 4 drives the screw 2 to rotate, causing the slide 3 to move on the screw. A bracket 5 is connected to the slide 3, and a clamping assembly is connected to the bracket 5 for clamping multiple piston rings at once for grinding. A second bracket 6 is connected to one end of the base 1, and the second bracket 6 has multiple placement positions for placing piston rings. The piston rings are placed side by side on the second bracket 6. When removing the piston rings, the clamping assembly moves with the slide 3 to the second bracket 6, clamping and removing the side-by-side piston rings at once.

[0028] Reference Appendix Figures 2-4The clamping assembly includes a rotating shaft 7 rotatably mounted on a bracket 5. The end of the rotating shaft 7 is connected to a rotating cylinder 8 by bolts. The rotating cylinder 8 is assembled to install the components inside the rotating cylinder 8. The rotating cylinder 8 is provided with a guide groove 801. The rotating shaft 7 has a coaxial main shaft 9 inside, and a blade plate 10 is connected to the main shaft 9. The blade plate 10 has a first sliding groove 101. The first sliding groove 101 contains a sliding shaft and a lifting member 11. The sliding shaft is connected to the lifting member 11. The lifting member 11 passes through the guide groove. One end of the lifting member 11 exposed outside the rotating cylinder 8 is connected to a fixed pawl 12. The fixed pawl 12 has a movable bottom clamping plate 13 inside. The bottom clamping plate 13 is connected to a guide post 14 that passes through the fixed pawl 12. The guide post 14 is connected to a wing plate 15. The wing plate 15 has a second sliding groove 151. The second sliding groove 151 also contains a sliding shaft. The two ends of the sliding shaft are connected to connecting plates 16. The fixed pawl 12 has a clearance groove 121. The connecting plate 16 passes through the clearance groove and is connected to a side clamping plate 17. The fixed jaw 12 is provided with a spring placement groove 122, and a spring 18 is placed inside the spring placement groove 122. The spring 18 is sleeved on the outside of the guide post 14, and a stop ring 19 is connected to the guide post 14. An electric push rod 20 is also connected to the bracket 5. One end of the main shaft 9 extends to the outside of the rotating shaft 7, and the output of the electric push rod 20 is connected to the rotating shaft 7 through a connecting rod.

[0029] The principle of the clamping assembly for gripping the piston rings is as follows: When the clamping assembly moves with the slide block 3 into the piston rings placed side by side, the electric push rod 20 actuates to generate a linear output, pushing the main shaft 9 to move axially. Based on the cooperation of the lifting member 11 through the guide groove, the lifting member 11 gradually moves away from the main shaft 9 through the cooperation with the slide groove 101, and the lifting member 11 gradually lifts; during the lifting process, the bottom clamping plate 13 first contacts the inner ring surface of the piston ring, and then maintains a state of contact with the inner ring surface of the piston ring, i.e., at the... In the stopped position, as the lifting member 11 continues to lift, the piston ring gradually enters the fixed chuck 12. The relative movement between the bottom clamping plate 13 and the fixed chuck 12 causes the spring 18 to be compressed, and the guide post 14 gradually extends out of the fixed chuck 12. During this process, the side clamping plate 17 gradually moves closer to the guide post 14 under the squeezing action of the sliding groove 151 of the wing plate 15, until the side clamping plates 17 tightly clamp the side wall of the piston ring. In this way, the side clamping plate 17 and the bottom clamping plate 13 together complete the tight clamping action of the piston ring.

[0030] As explained above regarding the clamping assembly's ability to grip the piston rings, the prerequisite for clamping is that the piston rings are placed side-by-side on the support 6, with the piston ring 21 secured at the placement position 22. After the clamping assembly clamps the piston ring 21, it cannot retract directly. In this embodiment, the axis of the side-by-side piston rings 21 is not collinear with the axis of the main shaft 9; the axis of the main shaft 9 is higher than the axis of the piston ring 21. When the clamping assembly moves into the piston ring, as the lifting member 11 rises, the upper clamping assembly first contacts the inner surface of the piston ring. Then, as it continues to lift, the bottom clamping plate 13 lifts the piston ring from the placement position 22. After the clamping assembly circumferentially clamps the piston ring, the piston ring is coaxial with the main shaft. At this point, the piston ring is suspended above the placement position, allowing it to retract for grinding operations. (Refer to Appendix) Figure 5 .

[0031] Reference Appendix Figure 1 and Figure 5 A bracket 23 is connected to the base 1, and a grinding roller 24 is mounted on the bracket 23. A gearbox 25 is also connected to the bracket 23. The input of the gearbox 25 is connected to a second motor 26. The gearbox 25 has two outputs. One output is connected to the grinding roller 24 to drive the grinding roller 24 to rotate at high speed to achieve the purpose of grinding the piston ring. The other output is an exposed output gear to drive the clamping assembly to rotate at a slow speed to achieve the purpose of grinding the entire outer ring surface of the piston ring. Specifically, a gear 27 is connected to the main shaft 9. The gear 27 meshes with the exposed output gear of the gearbox 25. The main shaft 9 and the gear 27 rotate synchronously. After the second motor 26 starts, the high-speed rotation output drives the grinding roller 24 to rotate at high speed. At the same time, the low-speed rotation output drives the main shaft 9 to rotate through the gear 27, so that the tightly clamped piston ring rotates slowly in a circumferential direction.

[0032] Reference Appendix Figure 5 A screw 28 is rotatably connected to the base 1, and a motor 29 is also fixed to the base 1. The screw 28 is connected to the output end of the motor 29, and the bracket 23 is fitted onto the screw 28. The motor 29 can control the position of the bracket 23 on the screw 28, thereby controlling the contact state between the grinding roller 24 and the piston ring. After grinding, when the clamping assembly places the ground piston ring into the placement position, the grinding roller 24 needs to disengage from the piston ring to prevent the side-moving piston ring from sliding against the grinding roller and causing scratches. In this embodiment, the bracket 26 can be easily slidably disassembled laterally. After the ground piston ring is returned to the placement position, the clamping assembly retracts and releases the piston ring. With external assistance, the piston ring is pressed down and locked in the placement position. At this time, the bracket for placing the piston ring on the bracket 2 can be slidably removed laterally, and the bracket for loading the piston ring to be ground can be replaced on the bracket 2.

[0033] Common sense dictates that a large amount of metal dust will be generated during the polishing process. In this embodiment, refer to the attached... Figure 7A dust cover 30 is connected to the base 1. During grinding, the dust cover can enclose the grinding roller 24 and piston rings to prevent dust from flying. A groove is opened on one side of the dust cover 30 for the gearbox 25 to be installed, and space is reserved for the gearbox to retract with the friction roller when it retracts. The relative sliding of the dust cover on the gearbox can also support the gearbox. A second clearance groove 301 is provided on the dust cover 30 along the axis of the main shaft for the sliding of the bracket 5.

[0034] Reference Appendix Figure 7 The dust cover 30 is equipped with a nozzle 31 at the bottom. The nozzle 31 draws gas from inside the dust cover under the action of an external fan, creating a negative pressure inside the dust cover. The dust generated during grinding will be drawn out of the device with the airflow, preventing dust from flying.

[0035] Reference Appendix Figure 2 The bracket 5 is connected to a side sealing plate 32, which moves together with the bracket 5 and cooperates with the dust cover 30 to ensure lateral sealing during grinding.

[0036] Reference Appendix Figure 8 The dust cover 30 is also connected to a motor 4 33, the output of which is connected to a gear 1 34. A column shaft 35 is connected to the outer wall of the dust cover 30, and a rotating cover 36 is rotatably mounted on the column shaft 35. A gear 2 37 is connected to the rotating cover 36, and the gear 2 37 is fitted onto the column shaft 35. The gear 2 37 meshes with the gear 1 34. A sealing strip 38 is connected to the rotating cover 36. After the clamping assembly retracts into place, the motor 4 33 starts to drive the rotating cover 36 to rotate and seal one side of the dust cover 30. At the same time, the sealing strip 38 also covers the clearance groove 2 301 to ensure the dustproof effect.

[0037] Reference Appendix Figure 9 and 10A brush 39 is connected to the inner wall of the dust cover 30. In this embodiment, the piston rings are polished round by round during the polishing process, and the brush can clean the polished surface in a timely manner. During the cleaning process, the brush 39 will be in close contact with the outer ring surface of the piston ring 21. In order to prevent the piston ring from squeezing the brush during the process of the piston ring 21 entering and exiting the dust cover 30, this embodiment performs a repositioning operation on the brush 39 during the process of the piston ring 21 entering and exiting the dust cover 30. Specifically, the dust cover 30 has a sliding groove 302, and a guide rod 40 is connected to the outer wall. The guide rod 40 lies across the sliding groove 302. A slider 41 is connected to the brush 39 and slides on the guide rod 40. One end of the guide rod 40 is connected to a limit cap 42. A spring 43 is sleeved on the guide rod 40 between the slider 41 and the limit cap 42. Multiple wire clips 44 are connected to the inner wall of the dust cover 30. The side wall of the dust cover 30 has a sliding groove 303. A slide rod 45 is provided at the sliding groove 303. The slider 41 is connected to the slide rod 45 through a pull wire 46. The pull wire 46 passes through each wire clip 44 and runs along the inner wall of the dust cover 30. One end of the slide rod 45 extends to the outside of the dust cover 30 and interacts with the rotating cover 36.

[0038] When the piston ring needs to move in and out of the dust cover 30, motor 4 33 first starts to drive the rotating cover 36 to rotate and open. After the cover 36 rotates and opens to the correct position, it will squeeze the slide rod 45 to move downward in the slide groove 2 303, and pull the slide head 41 back through the pull cable 46. The spring 2 43 is compressed, and the slide head 41 retracts, which means the brush 39 retracts, thus achieving the avoidance effect of the brush 39 when the piston ring moves in and out. After the rotating cover 36 is reset by motor 4 33, the elasticity of the spring 2 43 causes the slide rod 45 to reset. At the same time, under the elasticity of the spring 2 43, the brush 39 can be kept in close contact with the outer ring surface of the piston ring 21 to ensure the cleaning effect.

[0039] In this invention, a clamping assembly can simultaneously clamp and remove multiple piston rings. Simultaneously, the clamping assembly can rotate at a controlled slow speed, allowing for ring-by-ring grinding of the outer surface of the clamped piston rings, ensuring effective grinding. A dust cover and air nozzle collect the grinding dust, preventing leakage. The rotating cover on the side of the dust cover allows the piston rings to enter and exit when open, and when closed, it simultaneously covers the entry / exit channels and the second clearance groove on the side of the dust cover, ensuring dust prevention. Furthermore, when opened, it simultaneously retracts the brush, preventing the brush from obstructing the movement of the piston rings. After resetting, the brush adheres tightly to the piston rings to be ground, ensuring both cleaning and effective grinding.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An automatic piston ring circumferential grinding device, comprising a base (1), a screw (2) rotatably mounted on the base (1), a slide (3) mounted on the screw (2), a motor (4) connected to one side of the base (1), the screw (2) being connected to the output of the motor (4), a bracket (5) connected to the slide (3), and a second bracket (6) connected to one end of the base (1), the second bracket (6) having multiple placement positions for placing piston rings; characterized in that: A clamping assembly is connected to the bracket (5); The clamping assembly includes a rotating shaft (7) rotatably mounted on a support (5), with a rotating cylinder (8) connected to the end of the rotating shaft (7). The rotating cylinder (8) has a guide groove. A coaxial main shaft (9) is built into the rotating shaft (7). A blade plate (10) is connected to the main shaft (9). A sliding groove (101) is provided on the blade plate (10). A sliding shaft and a lifting member (11) are provided in the sliding groove (101). The sliding shaft is connected to the lifting member (11). The lifting member (11) passes through the guide groove. A fixed chuck (12) is connected to one end of the lifting member (11) exposed on the rotating cylinder (8). A movable bottom clamping plate (13) is provided inside the fixed chuck (12). A guide post (14) that passes through the fixed chuck (12) is connected to the bottom clamping plate (13). 14) is connected to a wing plate (15), and the wing plate (15) is provided with a second sliding groove (151). The second sliding groove (151) is provided with a sliding shaft, and the two ends of the sliding shaft are connected to a connecting plate (16). The fixed claw (12) is provided with a clearance groove (121). The connecting plate (16) passes through the clearance groove and is connected to a side clamp plate (17). The fixed claw (12) is provided with a spring placement groove (122). The spring placement groove (122) is provided with a spring (18). The spring (18) is sleeved on the outside of the guide post (14). The guide post (14) is connected to a stop ring (19). The bracket (5) is connected to an electric push rod (20). One end of the main shaft (9) extends to the outside of the rotating shaft (7). The output of the electric push rod (20) is connected to the rotating shaft (7).

2. The piston ring circumference automatic grinding device according to claim 1, characterized in that: A bracket (23) is connected to the base (1), a grinding roller (24) is provided on the bracket (23), and a gearbox (25) is also connected to the bracket (23). The input of the gearbox (25) is connected to the motor (26). The gearbox (25) has two outputs, one of which is connected to the grinding roller (24), and the other is an exposed output gear. A gear (27) is connected to the main shaft (9), and the gear (27) meshes with the exposed output gear of the gearbox (25).

3. The piston ring circumference automatic grinding device according to claim 2, characterized in that: The base (1) is rotatably connected to the screw two (28), and the base (1) is fixed with the motor three (29). The screw two (28) is connected to the output end of the motor three (29), and the bracket (23) is fitted on the screw two (28).

4. The piston ring circumference automatic grinding device according to claim 3, characterized in that: A dust cover (30) is connected to the base (1).

5. The piston ring circumference automatic grinding device according to claim 4, characterized in that: The dust cover (30) has a groove on one side for the gearbox (25) to be installed, and a second clearance groove (301) is provided along the axis of the main shaft for the bracket (5) to slide.

6. The piston ring circumference automatic grinding device according to claim 4 or 5, characterized in that: The dust cover (30) is equipped with a vent (31) at the bottom.

7. The piston ring circumference automatic grinding device according to claim 6, characterized in that: A side sealing plate (32) is connected to the bracket (5).

8. The piston ring circumference automatic grinding device according to claim 7, characterized in that: The dust cover (30) is also connected to a motor four (33), the output of the motor four (33) is connected to a gear one (34), a column shaft (35) is connected to the outer wall of the dust cover (30), a rotating cover (36) is rotatably provided on the column shaft (35), a gear two (37) is connected to the rotating cover (36), the gear two (37) is sleeved on the column shaft (35), the gear two (37) meshes with the gear one (34), and a seal (38) is connected to the rotating cover (36).

9. The piston ring circumference automatic grinding device according to claim 8, characterized in that: The dust cover (30) has a brush (39) attached to its inner wall.

10. The piston ring circumference automatic grinding device according to claim 9, characterized in that: The dust cover (30) has a sliding groove (302) and a guide rod (40) connected to its outer wall. The guide rod (40) is horizontally across the sliding groove (302). A slider (41) is connected to the brush (39) and slides on the guide rod (40). One end of the guide rod (40) is connected to a limit cap (42). A spring (43) is sleeved on the guide rod (40) between the slider (41) and the limit cap (42). The side wall of the dust cover (30) has a sliding groove (303) and a slider (45) is provided at the sliding groove (303). The slider (41) is connected to the slider (45) through a pull wire (46). One end of the slider (45) extends outside the dust cover (30) and interacts with the rotating cover (36).

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