A polishing device for taper-shank end mill machining with cleaning structure

Abstract

The utility model discloses a polishing treatment device of taper handle end mill processing with cleaning structure, including the casing, setting in the casing top and being used for clamping the rotating chuck of milling cutter of processing, setting in the casing top a pair of first linear guide rail, the mount of sliding setting in the top of first linear guide rail and setting on the mount and being used for polishing the polishing roller of milling cutter of processing, polishing treatment device still includes the scrap guide mechanism and the scraping mechanism, the scrap guide mechanism sliding sets up in the top of casing, and the scrap guide mechanism includes air pump, guide air baffle, rotating plate and rotating guide plate, air pump has a pair of and respectively sliding sets up in the top of casing, the lateral of air pump is provided with the guide air baffle, and the end face of guide air baffle is provided with a plurality of guide groove for guiding air and blowing to milling cutter of processing, the device solves the problem of the safety of user in the process of polishing that scrap splashes, reaches the effect that improves polishing efficiency and guarantees the safety of user.

Description

Technical Field

[0001] This utility model relates to the field of tapered shank end mill processing technology, and more specifically, it relates to a grinding device for processing tapered shank end mills with a cleaning structure. Background Technology

[0002] In the field of machining, tapered shank end mills are a commonly used cutting tool, and their machining quality directly affects the accuracy and efficiency of subsequent machining processes. Grinding is a key step in the machining process of tapered shank end mills. Grinding can effectively remove burrs, oxide layers, and microscopic defects generated during machining from the end mill surface, improving the surface finish and cutting edge sharpness of the end mill, thereby ensuring the cutting performance and durability of the end mill in actual use.

[0003] Currently, a common problem with grinding devices used for taper shank end mills on the market is the difficulty in effectively shielding and guiding the waste chips generated during the grinding process. During grinding, the high-speed friction between the grinding roller and the end mill generates a large amount of metal waste chips. These chips possess high kinetic energy and fly in all directions and at irregular speeds.

[0004] On the one hand, the flying debris lacks effective protective measures and can easily splash directly onto operators, causing damage to their skin and eyes, seriously affecting their personal safety. For example, small metal shavings may enter the eyes, causing eye inflammation or even more serious vision damage; larger shavings may scratch the skin, causing external wound infection.

[0005] On the other hand, due to the lack of a reasonable guiding structure, the waste will be scattered randomly in the work area during the splashing process, which not only makes the working environment dirty and messy, but also increases the difficulty and cost of subsequent cleaning work and reduces production efficiency. Utility Model Content

[0006] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a grinding treatment device for machining tapered shank end mills with a cleaning structure that can guide waste chips toward the adsorption part.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This utility model is further configured as follows: it includes a housing, a rotary chuck disposed on the top of the housing for holding the milling cutter to be processed, a pair of first linear guide rails disposed on the top of the housing, a mounting bracket slidably disposed on the top of the first linear guide rails, and a grinding roller disposed on the mounting bracket for grinding the milling cutter to be processed. The grinding device also includes a waste chip guiding mechanism and a scraping mechanism. The waste chip guiding mechanism is slidably disposed on the top of the housing and includes an air pump, a guide vane, a rotating plate, and a rotating guide plate. The air pump has a pair and is slidably disposed on the top of the housing. The guide vane is disposed beside the air pump, and the end face of the guide vane has multiple guide grooves for guiding air and blowing it toward the milling cutter to be processed. The rotating plate is rotatably disposed beside the guide vane. The rotating guide plate is slidably disposed beside the rotating plate, and the side of the rotating plate has a stroke chamber for limiting the sliding of the rotating guide plate. When the rotating plate rotates, the rotating guide plate can slide and is in a shielding state toward the milling cutter to be processed. The scraping mechanism is disposed on the top of the housing and is used to scrape off the waste chips generated after grinding.

[0009] By adopting the above technical solution, the problem of debris splashing during the grinding process affecting user safety has been solved, achieving the effect of improving grinding efficiency and ensuring user safety.

[0010] The present invention is further configured such that: the waste guiding mechanism includes a first shielding plate and a second shielding plate; the first shielding plate has a pair and is slidably disposed on the top of the housing, and when the first shielding plate slides, it can form an air guiding area with the rotating guide plate in the flipped state; the second shielding plate is slidably disposed on the top of the housing, and when the second shielding plate slides, it can form a waste guiding area with the second shielding plate.

[0011] The present invention is further configured such that: the waste guide mechanism also includes a connecting part and a second linear guide rail; the connecting part has a pair and is respectively disposed on the side of the mounting frame, and the bottom of the air pump is connected to the connecting part by fasteners; the second linear guide rail has a pair and is respectively disposed on the top of the housing, and the pair of second linear guide rails are located on both sides of the rotating chuck, and the connecting part and the second linear guide rail are slidably engaged, so that when the mounting frame slides, the air pump can be driven to move synchronously through the connecting part.

[0012] The present invention is further configured such that: the waste guide mechanism includes a rotary driver, a first telescopic cylinder, a positioning rod, and an ejector; the rotary driver has a pair and is respectively disposed on the top of the connecting part, and the output end of the rotary driver is connected to the rotating plate, so that when the rotary driver is started, it can drive the rotating plate to a flipped state; the first telescopic cylinder has a pair and is respectively disposed on the top of the rotating plate; the positioning rod is rotatably disposed on the top of the rotating guide plate; the ejector is disposed on the output end of the first telescopic cylinder, and the ejector is rotatably connected to the positioning rod.

[0013] The present invention is further configured such that: the waste guiding mechanism includes a positioning part, a second telescopic cylinder and an adsorption part; the positioning part has a pair and is respectively disposed on the side of the mounting frame, and when the mounting frame slides, it can drive the positioning part to move synchronously, and the bottom of the positioning part is slidably connected to the second linear guide rail, and the bottom of the positioning part is connected to the second protective plate, and when the mounting frame slides, it can drive the positioning part and the second protective plate to move synchronously and drive the second protective plate and the first protective plate to form a waste guiding area; the adsorption part is disposed on the top of the housing, and the adsorption part is located on the side of the second protective plate.

[0014] The present invention is further configured such that: the scraping mechanism includes a mounting frame, a first scraper and a second scraper; the mounting frame has a pair and is respectively mounted on the side of the positioning part; the first scraper has a pair and is respectively disposed on the side of the pair of mounting frames, and the end face of the first scraper is in contact with the end face of the adsorption part; the second scraper has a pair and is respectively slidably disposed on the side of the first scraper.

[0015] The present invention is further configured such that: the scraping mechanism includes a guide portion and a return spring; the guide portion has a pair and is slidably mounted on the side of the mounting frame, and the guide portion and the mounting frame are in clearance fit; the return spring has a pair and is disposed on the outside of the guide portion, one end of the return spring is fixed to the mounting frame, and the other end of the return spring is fixed to the second scraper.

[0016] By adopting the above technical solution, the first scraper and the second scraper scrape together and clean the waste debris adsorbed on the adsorption section.

[0017] In summary, this application includes at least one of the following beneficial technical effects:

[0018] By setting up a waste chip guiding mechanism, the problem of waste chip splashing during the grinding process affecting user safety was solved, achieving the effect of improving grinding efficiency and ensuring user safety.

[0019] By setting up a scraping mechanism, waste debris can be automatically cleaned up without the need for manual cleaning of the adsorption unit. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of a grinding device for machining tapered shank end mills with a cleaning structure according to the present invention.

[0021] Figure 2 This is a three-dimensional structural diagram of a grinding device for machining tapered shank end mills with a cleaning structure, wherein the rotating guide plate is unfolded and the first and second shielding plates are close together.

[0022] Figure 3 This is a front view of a grinding device with a cleaning structure for machining tapered shank end mills according to the present invention.

[0023] Figure 4 This is a partial three-dimensional structural diagram of a grinding device for machining tapered shank end mills with a cleaning structure, in which the grinding rollers are relatively far apart and the rotating guide plate is retracted.

[0024] Figure 5 This is a top view of a grinding device with a cleaning structure for machining tapered shank end mills according to the present invention.

[0025] Figure 6 This is a three-dimensional structural diagram of the air guide plate of a grinding device for machining tapered shank end mills with a cleaning structure according to this utility model.

[0026] Figure 7 This is a three-dimensional structural diagram of the scraping mechanism of a grinding device with a cleaning structure for machining tapered shank end mills according to the present invention;

[0027] Figure 8 This is a three-dimensional structural diagram of the guide section and return spring of a grinding device for machining a tapered shank end mill with a cleaning structure according to this utility model.

[0028] Explanation of reference numerals in the attached drawings: 1. Housing; 2. Rotary chuck; 3. First linear guide rail; 4. Mounting bracket; 5. Grinding roller; 6. Waste chip guiding mechanism; 61. Air pump; 62. Guide vane; 63. Rotating plate; 64. Rotating guide plate; 65. First shielding plate; 66. Second shielding plate; 67. Connecting part; 68. Second linear guide rail; 69. Rotary driver; 691. First telescopic cylinder; 692. Positioning rod; 693. Ejection part; 694. Positioning part; 695. Second telescopic cylinder; 696. Adsorption part; 7. Scraping mechanism; 71. Setting frame; 72. First scraper; 73. Second scraper; 74. Guide part; 75. Return spring. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] Please see Figure 1-8 The present invention provides the following technical solution:

[0032] Embodiment 1 includes a housing 1, a rotary chuck 2 disposed on the top of the housing 1 for holding a milling cutter to be processed, a pair of first linear guide rails 3 disposed on the top of the housing 1, a mounting bracket 4 slidably disposed on the top of the first linear guide rails 3, and a grinding roller 5 disposed on the mounting bracket 4 for grinding the milling cutter to be processed. The grinding device also includes a waste chip guiding mechanism 6 and a scraping mechanism 7. The waste chip guiding mechanism 6 is slidably disposed on the top of the housing 1 and includes an air pump 61, a guide vane 62, a rotating plate 63, and a rotating guide plate 64. The air pump 61 has a pair of rollers slidably disposed on the top of the housing 1. The top of the machine housing 1 is equipped with a guide vane 62 located beside the air pump 61. The end face of the guide vane 62 has multiple guide grooves for guiding air and blowing it toward the milling cutter to be processed. A rotating plate 63 is rotatably located beside the guide vane. A rotating guide plate 64 is slidably located beside the rotating plate 63. A stroke chamber for limiting the sliding of the rotating guide plate 64 is provided beside the rotating plate 63. When the rotating plate 63 rotates, the rotating guide plate 64 can slide and shield the direction of the milling cutter to be processed. A scraping mechanism 7 is located on the top of the machine housing 1. The scraping mechanism 7 is used to scrape off the waste generated after grinding.

[0033] Specifically, the top of the mounting frame 4 is equipped with a hydraulic cylinder for driving the mounting frame 4 to slide up or down on the top of the first linear guide rail 3. When the hydraulic cylinder is activated, it can adjust the position of the mounting frame 4 on the first linear guide rail 3, thereby better adapting to the grinding work of the milling cutter to be processed. A rotary motor is provided on the side of the first linear guide rail 3 for driving the mounting frame 4 to slide towards the rotary chuck 2. When the rotary motor is activated, it can drive the mounting frame 4 to slide horizontally along the first linear guide rail 3. This is existing technology and will not be described in detail here. First, the milling cutter to be processed is placed on the rotary chuck 2. Then, the rotary chuck 2 clamps and fixes the milling cutter to be processed. Then, the mounting frame 4 slides along the first linear guide rail 3 towards the rotary chuck 2 until the grinding roller 5 is in contact with the milling cutter to be processed. After that, the grinding roller 5 rotates, thereby grinding both sides of the milling cutter to be processed. The top of the mounting frame 4 is equipped with a first motor for driving the grinding roller to rotate, and the bottom of the housing 1 is equipped with a second motor connected to the bottom of the rotary chuck 2. Both the first and second motors are preferably servo motors, thereby achieving rotary grinding of the milling cutter to be processed and improving grinding efficiency. To reduce the impact of flying debris during grinding, when the mounting bracket 4 slides towards the rotating chuck 2, the mounting bracket 4 drives the air pump 61 to move synchronously. The air pump 61 then starts and blows air towards the debris generated during the process through the guide vane 62, ensuring the debris is blown in a consistent direction. It should be noted that in this state, the grinding roller 5 is already in contact with the milling cutter to be processed. At this time, the rotating plate 63 rotates and drives the rotating guide plate 64 to rotate synchronously until the rotating plate 63 flips over. Then, the rotating guide plate 64 slides away from the rotating plate 63. In this state, the pair of rotating guide plates 64 form an angle, allowing the air blown by the air pump 61 to be directed towards the milling cutter during grinding and blowing the debris away from the air pump 61. This avoids the debris generated during grinding flying directly towards the user, solving the problem of debris flying affecting user safety during grinding and achieving the effect of improving grinding efficiency and ensuring user safety.

[0034] See Figures 3-5 The waste guiding mechanism 6 also includes a first shielding plate 65 and a second shielding plate 66; the first shielding plate 65 has a pair and is slidably disposed on the top of the housing 1 respectively, and when the first shielding plate 65 slides, it can form an air guiding area with the rotating guide plate 64 in the flipped state; the second shielding plate 66 is slidably disposed on the top of the housing 1, and when the second shielding plate 66 slides, a waste guiding area can be formed between the second shielding plate 66 and the second shielding plate 66.

[0035] Specifically, when the rotating guide plate 64 is open and the grinding roller 5 is in contact with the milling cutter to be processed, the first shielding plate 65 rises and cooperates with the rotating guide plate 64 in the open state to form an air guiding area. Then, when the mounting frame 4 moves, it can drive the second shielding plate 66 to move synchronously. This allows the rotating guide plate 64, the first shielding plate 65 and the second shielding plate 66 to jointly form a guiding chamber for guiding the flow direction of waste chips when the grinding roller 5 is performing grinding work. This causes the waste chips generated during the grinding process to be blown away from the air pump 61. In order to ensure the guiding effect of waste chips, the user can also set a shield on the top of the mounting frame 4 to prevent waste chips from flowing above the rotary chuck 2.

[0036] See Figure 3 The waste guide mechanism 6 also includes a connecting part 67 and a second linear guide rail 68; the connecting part 67 has a pair and is respectively disposed on the side of the mounting frame 4, and the bottom of the air pump 61 is connected to the connecting part 67 by fasteners; the second linear guide rail 68 has a pair and is respectively disposed on the top of the housing 1, and the pair of second linear guide rails 68 are located on both sides of the rotating chuck 2, and the connecting part 67 and the second linear guide rail 68 are slidably engaged, so that when the mounting frame 4 slides, the air pump 61 can be driven to move synchronously through the connecting part 67.

[0037] Specifically, to ensure that the air pump 61 can move synchronously when the mounting bracket 4 moves, the connecting part 67 is fixedly connected to the mounting bracket 4, and the second linear guide rail 68 is slidably engaged with the connecting part 67. This allows the air pump 61 to move synchronously through the connecting part 67 when the mounting bracket 4 moves.

[0038] See Figure 6 and Figure 7 The waste guide mechanism 6 also includes a rotary driver 69, a first telescopic cylinder 691, a positioning rod 692, and an ejector 693. The rotary driver 69 has a pair and is respectively disposed on the top of the connecting part 67, and the output end of the rotary driver 69 is connected to the rotating plate 63. When the rotary driver 69 is started, it can drive the rotating plate 63 to a flipped state. The first telescopic cylinder 691 has a pair and is respectively disposed on the top of the rotating plate 63. The positioning rod 692 is rotatably disposed on the top of the rotating guide plate 64. The ejector 693 is disposed on the output end of the first telescopic cylinder 691, and the ejector 693 is rotatably connected to the positioning rod 692.

[0039] Specifically, to drive the rotating plate 63 to rotate and the rotating guide plate 64 to move, the rotary driver 69 is activated and drives the rotating plate 63 to rotate during the grinding process. After rotation, the first telescopic cylinder 691 is activated and drives the rotating guide plate 64 to extend outward from the rotating plate 63 through the ejector part 693 and the positioning rod 692, thereby protecting the grinding roller 5 and the milling cutter to be processed during the grinding process. In this state, the rotating guide plate 64 and the first shielding plate 65 form an air guiding area.

[0040] See Figure 6 and Figure 7 The waste guide mechanism 6 also includes a positioning part 694, a second telescopic cylinder 695, and an adsorption part 696. The positioning part 694 has a pair and is respectively disposed on the side of the mounting frame 4. When the mounting frame 4 slides, it can drive the positioning part 694 to move synchronously. The bottom of the positioning part 694 is slidably connected to the second linear guide rail 68 and the bottom of the positioning part 694 is connected to the second shielding plate 66. When the mounting frame 4 slides, it can drive the positioning part 694 and the second shielding plate 66 to move synchronously and drive the second shielding plate 66 and the first shielding plate 65 to form a waste guide area. The adsorption part 696 is disposed on the top of the housing 1 and is located on the side of the second shielding plate 66.

[0041] Specifically, to raise the second shielding plate 66, when the grinding roller 5 is in contact with the milling cutter to be processed, the second telescopic cylinder 695 is activated and drives the second shielding plate 66 to rise. In this state, a guide chamber is formed between the rotating guide plate 64, the first shielding plate 65, and the second shielding plate 66 to guide the flow direction of the waste chips. Then, the air pump 61 is activated and blows the waste chips toward the adsorption section 696. The adsorption section 696 is preferably powered by an electromagnet. The electromagnet can adsorb the blown waste chips, thereby achieving the guidance and adsorption collection of the waste chips.

[0042] See Figure 7 and Figure 8 The scraping mechanism 7 includes a mounting frame 71, a first scraper 72, and a second scraper 73. The mounting frame 71 is a pair and is respectively mounted on the side of the positioning part 694. The first scraper 72 is a pair and is respectively disposed on the side of the pair of mounting frames 71, and the end face of the first scraper 72 is in contact with the end face of the adsorption part 696. The second scraper 73 is a pair and is respectively slidably disposed on the side of the first scraper 72.

[0043] Specifically, when the mounting frame 4 moves, it can drive the setting frame 71, the first scraper 72, and the second scraper 73 to move synchronously. When the grinding work is completed and the mounting frame 4 slides away from the rotating chuck 2, the electromagnet is turned off in this state, and then the first scraper 72 and the second scraper 73 scrape off the waste adsorbed on the adsorption part 696.

[0044] See Figure 7 and Figure 8 The scraping mechanism 7 also includes a guide portion 74 and a return spring 75; the guide portion 74 has a pair and is slidably mounted on the side of the mounting frame 71, and the guide portion 74 and the mounting frame 71 are in clearance fit; the return spring 75 has a pair and is disposed on the outside of the guide portion 74, one end of the return spring 75 is fixed to the mounting frame 71, and the other end of the return spring 75 is fixed to the second scraper 73.

[0045] Specifically, to prevent motion interference caused by the continued movement of the pair of second scrapers 73 after contact, the guide portion 74 is driven to slide away from the first scraper 72 when the pair of second scrapers 73 contact, and the return spring 75 is in a compressed state in this state. Both the first scraper 72 and the second scraper 73 are fitted with flexible cleaning portions, which can be quickly installed and removed from the first scraper 72 and the second scraper 73 via fasteners.

[0046] Obviously, the embodiments described above are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

Claims

1. A grinding device for machining tapered shank end mills with a cleaning structure, comprising a housing (1), a rotary chuck (2) disposed on the top of the housing (1) for clamping the end mill to be machined, a pair of first linear guides (3) disposed on the top of the housing (1), a mounting bracket (4) slidably disposed on the top of the first linear guides (3), and a grinding roller (5) disposed on the mounting bracket (4) for grinding the end mill to be machined, characterized in that: The grinding and processing device also includes a waste chip guiding mechanism (6) and a scraping mechanism (7); The waste chip guiding mechanism (6) is slidably disposed on the top of the housing (1). The waste chip guiding mechanism (6) includes an air pump (61), a guide vane (62), a rotating plate (63), and a rotating guide plate (64). The air pump (61) has a pair and is slidably disposed on the top of the housing (1); The guide vane (62) is located on the side of the air pump (61), and the end face of the guide vane (62) is provided with multiple guide grooves for guiding air and blowing it toward the milling cutter to be processed. The rotating plate (63) is rotatably mounted on the side of the air guide plate; The rotating guide plate (64) is slidably disposed on the side of the rotating plate (63), and a stroke chamber for limiting the sliding of the rotating guide plate (64) is provided on the side of the rotating plate (63). When the rotating plate (63) rotates, the rotating guide plate (64) can slide and be in a shielding state towards the milling cutter to be processed. The scraping mechanism (7) is located on the top of the housing (1) and is used to scrape off the waste generated after grinding.

2. The grinding device for machining tapered shank end mills with a cleaning structure according to claim 1, characterized in that: The waste guiding mechanism (6) also includes a first shield (65) and a second shield (66); the first shield (65) has a pair and is slidably disposed on the top of the housing (1), and when the first shield (65) slides, it can form an air guiding area with the rotating guide plate (64) in the flipped state; the second shield (66) is slidably disposed on the top of the housing (1), and when the second shield (66) slides, it can form a waste guiding area with the second shield (66).

3. The grinding device for machining tapered shank end mills with a cleaning structure according to claim 1, characterized in that: The waste guide mechanism (6) also includes a connecting part (67) and a second linear guide (68); the connecting part (67) has a pair and is respectively disposed on the side of the mounting frame (4), and the bottom of the air pump (61) is connected to the connecting part (67) by fasteners; the second linear guide (68) has a pair and is respectively disposed on the top of the housing (1), and the pair of second linear guides (68) are located on both sides of the rotating chuck (2), and the connecting part (67) and the second linear guide (68) slide together, so that when the mounting frame (4) slides, the air pump (61) can be driven to move synchronously through the connecting part (67).

4. The grinding device for machining tapered shank end mills with a cleaning structure according to claim 3, characterized in that: The waste guide mechanism (6) also includes a rotary driver (69), a first telescopic cylinder (691), a positioning rod (692), and an ejector (693); the rotary driver (69) has a pair and is respectively disposed on the top of the connecting part (67), and the output end of the rotary driver (69) is connected to the rotating plate (63), and when the rotary driver (69) is started, it can drive the rotating plate (63) to flip; the first telescopic cylinder (691) has a pair and is respectively disposed on the top of the rotating plate (63); the positioning rod (692) is rotatably disposed on the top of the rotating guide plate (64); the ejector (693) is disposed on the output end of the first telescopic cylinder (691), and the ejector (693) is rotatably connected to the positioning rod (692).

5. A grinding device for machining tapered shank end mills with a cleaning structure according to any one of claims 1-4, characterized in that: The waste guide mechanism (6) also includes a positioning part (694), a second telescopic cylinder (695), and an adsorption part (696); the positioning part (694) has a pair and is respectively disposed on the side of the mounting frame (4). When the mounting frame (4) slides, it can drive the positioning part (694) to move synchronously. The bottom of the positioning part (694) is slidably connected to the second linear guide rail (68), and the bottom of the positioning part (694) is connected to the second shield plate (66). When the mounting frame (4) slides, it can drive the positioning part (694) and the second shield plate (66) to move synchronously and drive the second shield plate (66) and the first shield plate (65) to form a waste guide area; the adsorption part (696) is disposed on the top of the housing (1), and the adsorption part (696) is located on the side of the second shield plate (66).

6. The grinding device for machining tapered shank end mills with a cleaning structure according to claim 1, characterized in that: The scraping mechanism (7) includes a mounting frame (71), a first scraper (72), and a second scraper (73); the mounting frames (71) are in pairs and are respectively mounted on the side of the positioning part (694); the first scrapers (72) are in pairs and are respectively disposed on the side of the pair of mounting frames (71), and the end face of the first scraper (72) is in contact with the end face of the adsorption part (696); the second scrapers (73) are in pairs and are respectively slidably disposed on the side of the first scraper (72).

7. The grinding device for machining tapered shank end mills with a cleaning structure according to claim 6, characterized in that: The scraping mechanism (7) also includes a guide (74) and a return spring (75); the guide (74) has a pair and is slidably mounted on the side of the mounting frame (71), and the guide (74) and the mounting frame (71) are in clearance fit; the return spring (75) has a pair and is disposed on the outside of the guide (74), one end of the return spring (75) is fixed to the mounting frame (71), and the other end of the return spring (75) is fixed to the second scraper (73).

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