A keyway processing device for special-shaped welded pipe mold

Abstract

The utility model provides a special-shaped welded pipe mold keyway processing device, comprising a special-shaped welded pipe rolling roller and a positioning keyway, the positioning keyway is opened on the annular side of the special-shaped welded pipe rolling roller, a grinding component for removing burrs on the upper end of the positioning keyway is arranged on the front side of the fixed back plate, and a dust suction component for sucking most of the dust generated during the grinding process is arranged inside the processing box. The utility model enables a driving motor to drive the grinding wheel to rotate through a transmission shaft, so that a staff member holds the special-shaped welded pipe rolling roller and brings the positioning keyway close to the lower side of the annular side of the grinding wheel for grinding and deburring. In this process, when the fixing nut is loosened, the telescopic plate can be pulled to extend it, thereby increasing the shielding area of ​​the shielding plate, and when the low-speed motor is controlled to rotate forward or reverse, the vertical screw rod can drive the shielding plate to move up and down through the extension plate, so that the staff member can adjust the use height of the shielding plate according to their own needs.

Description

Technical Field

[0001] The utility model relates to the technical field of keyway processing of special-shaped welded pipe moulds, in particular to a keyway processing device for special-shaped welded pipe moulds. Background Art

[0002] The special-shaped welded pipe roller mold is in the shape of a roller, and the center of the roller has an axial through hole for being mounted on the main shaft. The through hole of the roller needs to be mounted on the main shaft with a key, so a keyway needs to be opened on the roller.

[0003] The keyways on the special-shaped welded pipe rolling rollers in the prior art are all processed by milling machines. Since burrs will remain on the upper end of the keyway after processing, the staff is required to use a grinding device to grind and remove the burrs on the upper end of the keyway to ensure the assembly accuracy of the keyway. However, the shielding covers on the existing grinding devices are mostly fixed structures, and the staff cannot adjust the shielding range and use height of the shielding covers according to their own needs. In addition, most of the existing grinding devices are not equipped with a dust suction structure to suck the dust generated during the grinding process, and the floating dust will affect the health of the surrounding staff, and the practicality is poor. Utility Model Content

[0004] The utility model aims to provide a keyway processing device for a special-shaped welded pipe die to solve the problems raised in the above-mentioned background technology.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A device for processing a keyway of a special-shaped welded pipe mold comprises a fixed base plate, a processing box, a special-shaped welded pipe roller and a positioning keyway, wherein the upper end face of the fixed base plate is fixedly connected to the processing box, the upper side of the rear end face of the processing box is fixedly connected to a fixed back plate, a special-shaped welded pipe roller is placed on the upper end of the processing box, a positioning keyway is provided on the annular side face of the special-shaped welded pipe roller, a grinding component for removing burrs on the upper end of the positioning keyway is provided on the front side of the fixed back plate, and a dust suction component for sucking most of the dust generated during the grinding process is provided inside the processing box.

[0007] Preferably, the grinding assembly includes a grinding wheel, a motor support, a drive motor and a transmission shaft. The upper side of the rear end surface of the fixed back plate is fixedly connected to the motor support, the rear end surface of the motor support is installed with the drive motor, the front end of the drive motor is connected to the transmission shaft, the front end of the transmission shaft is installed with a grinding wheel, and a protective mesh is placed on the upper end surface of the processing box.

[0008] Preferably, the dust suction assembly includes a first pulley, a second pulley, a driven shaft, a suction fan blade, a connecting vertical shaft, a driven bevel gear, a driving bevel gear and a protective shell, a first pulley is arranged on the rear side of the annular side surface of the transmission shaft, a second pulley is installed below the first pulley, a driven shaft is arranged at the front end of the second pulley, a driving bevel gear is arranged at the front end of the driven shaft, a driven bevel gear is meshed with the lower side of the annular side surface of the driving bevel gear, a connecting vertical shaft is connected to the middle position of the lower end surface of the driven bevel gear, a suction fan blade is installed at the lower end of the connecting vertical shaft, and a protective shell is installed on the upper side of the interior of the processing box.

[0009] Preferably, a low-speed motor is installed on the upper surface of the fixed back plate, a vertical screw is connected to the lower end of the low-speed motor, an extension plate is arranged on the lower side of the annular side of the vertical screw, and a shield plate is connected to the front end of the extension plate.

[0010] Preferably, a telescopic plate is inserted inside the shielding plate, and the telescopic plate and the shielding plate are both arc-shaped, an externally threaded rod is provided on the rear side of the upper end surface of the telescopic plate, a fixing nut is installed on the annular side of the externally threaded rod, a groove is provided on the upper end surface of the shielding plate, and the groove matches the externally threaded rod, and an internally threaded through hole is provided on the rear side of the inner part of the extension plate.

[0011] Preferably, an air guide shell is fixedly connected to the lower side of the interior of the processing box, a dust filter bag is installed on the lower side of the annular side of the air guide shell, and a fixed throat clamp is installed on the upper side of the annular side of the dust filter bag. An exhaust cavity is opened on the lower side of the rear end face of the processing box, a box door is installed on the lower side of the front end face of the processing box, and a limiting groove is opened on the upper side of the front end face of the fixed back plate.

[0012] Preferably, a first follower ring is provided on the annular side of the driven shaft, a first limit stop cover is installed on the upper side of the rear end surface of the processing box, a second follower ring is provided on the annular side of the connecting vertical shaft, a sealing bottom plate is installed on the bottom of the protective shell, support rods are symmetrically provided on the left and right sides and the front and rear sides of the annular side of the protective shell, and a transmission belt is provided between the first pulley and the second pulley.

[0013] Compared with the prior art, the beneficial effects of the utility model are:

[0014] 1. When the staff uses the rotating grinding wheel to grind and deburr the positioning key slot, the shield plate will block the debris flying upwards during the grinding process to prevent the flying debris from injuring the staff's face. When the fixing nut is loosened, the telescopic plate can be pulled to extend it, thereby increasing the shielding area of ​​the shield plate. When the low-speed motor is controlled to rotate forward or reverse, the vertical screw rod can drive the shield plate to move up and down through the extension plate, so that the staff can adjust the use height of the shield plate according to their own needs, which is practical.

[0015] 2. In the present invention, when the driving motor drives the grinding wheel to rotate through the transmission shaft, the transmission shaft will drive the first pulley to rotate, so that the first pulley drives the active bevel gear to rotate through the transmission belt, the second pulley and the driven shaft, and the active bevel gear drives the suction fan blades to rotate through the driven bevel gear and the connecting vertical shaft. At this time, the rotating suction fan blades will generate negative pressure on the upper side of the processing box to suck most of the dust above through the protective mesh plate, and the sucked dust will be concentratedly guided by the air guide shell to the dust filter bag for filtration, so as to prevent the dust generated during the grinding process from floating around and hurting the health of the staff. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the main structure of the utility model;

[0017] Figure 2 It is a structural diagram of the grinding component in the utility model;

[0018] Figure 3 It is a left side cross-sectional view of the grinding component and the dust collecting component in the utility model;

[0019] Figure 4 It is a partial structural diagram of the grinding component and the dust collection component in the utility model;

[0020] Figure 5 It is a partial structural diagram of the grinding component in the utility model.

[0021] In the figure: 1, fixed base plate; 2, processing box; 21, box door; 22, first limit stop cover; 3, grinding assembly; 31, protective mesh plate; 32, grinding wheel; 33, telescopic plate; 331, external thread rod; 332, fixing nut; 34, shielding plate; 341, slot; 35, extension plate; 351, internal thread through hole; 36, vertical screw rod; 37, low speed motor; 38, motor support; 39, drive motor; 311, transmission shaft; 4, special-shaped welded pipe roller; 5, positioning keyway; 6 , fixed back plate; 61, limit groove; 7, dust suction assembly; 71, first pulley; 72, transmission belt; 73, second pulley; 74, driven shaft; 741, first follower ring; 75, air guide shell; 76, exhaust chamber; 77, dust filter bag; 771, fixed throat clamp; 78, suction fan blade; 79, connecting vertical shaft; 791, second follower ring; 711, driven bevel gear; 712, driving bevel gear; 713, protective shell; 7131, support rod; 7132, blocking bottom plate. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] See also Figure 1-5 , the utility model provides a technical solution:

[0024] Embodiment 1:

[0025] A special-shaped welded pipe mold keyway processing device includes a fixed base plate 1, a processing box 2, a special-shaped welded pipe rolling roller 4 and a positioning keyway 5. The upper end surface of the fixed base plate 1 is fixedly connected to the processing box 2, and the fixed base plate 1 and the processing box 2 are connected by welding. The fixed base plate 1 is fixed to the ground by external expansion bolts. The processing box 2 supports the fixed back plate 6. The upper side of the rear end surface of the processing box 2 is fixedly connected to the fixed back plate 6. The fixed back plate 6 supports the grinding component 3. A control panel is installed on the left side of the front end surface of the processing box 2, and the control panel is respectively connected to the low-speed motor 37 and the drive motor 39 through wires. The control panel facilitates the staff to control the operation of the low-speed motor 37 and the drive motor 39. Since the internal detailed structure and working principle of the control panel are relatively mature technologies in the prior art, they will not be described in detail here.

[0026] A special-shaped welded pipe roller 4 is placed on the upper end of the processing box 2, a positioning key groove 5 is opened on the annular side of the special-shaped welded pipe roller 4, a grinding component 3 for removing burrs on the upper end of the positioning key groove 5 is arranged on the front side of the fixed back plate 6, and a dust suction component 7 for sucking most of the dust generated during the grinding process is arranged inside the processing box 2.

[0027] The grinding assembly 3 includes a grinding wheel 32, a motor support 38, a drive motor 39 and a transmission shaft 311. The upper side of the rear end surface of the fixed back plate 6 is fixedly connected with the motor support 38. The motor support 38 is L-shaped. The motor support 38 is connected to the fixed back plate 6 by welding. The motor support 38 supports the drive motor 39. The drive motor 39 is installed on the rear end surface of the motor support 38. When the drive motor 39 is working, it drives the transmission shaft 311 to rotate. The front end of the drive motor 39 is connected with the transmission shaft 311. The transmission shaft 311 is connected to the first pulley 71. The two processing boxes 2 are connected by welding, and the transmission shaft 311 will drive the first pulley 71 and the grinding wheel 32 to rotate. The grinding wheel 32 is installed at the front end of the transmission shaft 311. When the grinding wheel 32 rotates, it is convenient for the staff to grind and remove the burrs on the upper end of the keyway. A protective mesh plate 31 is placed on the upper end face of the processing box 2. The protective mesh plate 31 is not only convenient for the special-shaped welded pipe roller 4 to be placed on the upper end of the processing box 2, but also convenient for dust to enter the interior of the processing box 2. A low-speed motor 37 is installed on the upper end face of the fixed back plate 6. The low-speed motor 37 will drive the vertical screw 36 to rotate at a low speed when working.

[0028] A vertical screw rod 36 is connected to the lower end of the low-speed motor 37. The vertical screw rod 36 will drive the extension plate 35 to move up and down when rotating forward and reversely. An extension plate 35 is arranged on the lower side of the annular side of the vertical screw rod 36. The extension plate 35 is connected to the shield plate 34 by welding. The extension plate 35 will support the shield plate 34. The front end of the extension plate 35 is connected to the shield plate 34. The shield plate 34 is arc-shaped. The arc-shaped shield plate 34 will block the debris flying upwards during the grinding process, so as to ensure the safety during the grinding process. A telescopic plate 33 is inserted inside the shield plate 34, and the telescopic plate 33 is arc-shaped. The arc-shaped telescopic plate 33 can further increase the shielding area of ​​the shield plate 34 when extended.

[0029] An externally threaded rod 331 is provided on the rear side of the upper end surface of the telescopic plate 33, and the externally threaded rod 331 is connected to the telescopic plate 33 by welding. A fixing nut 332 is installed on the annular side of the externally threaded rod 331. The externally threaded rod 331 and the fixing nut 332 are convenient for fixing the telescopic plate 33. The fixing nut 332 is a butterfly nut, which is convenient for the staff to tighten or loosen it by hand. A slot 341 is provided on the upper end surface of the shielding plate 34, and the slot 341 matches the externally threaded rod 331. The slot 341 facilitates the externally threaded rod 331 to move back and forth inside the shielding plate 34 An internal threaded through hole 351 is provided on the rear side of the extension plate 35, and the internal threaded through hole 351 is meshed with the vertical screw rod 36. The internal threaded through hole 351 facilitates the rotation of the vertical screw rod 36 to drive the extension plate 35 to move up and down. A limiting groove 61 is provided on the upper side of the front end surface of the fixed back plate 6, and the limiting groove 61 matches the extension plate 35. The limiting groove 61 will limit the extension plate 35 to prevent the extension plate 35 from deflecting or shaking during the lifting and use process. An insertion cavity is provided inside the shielding plate 34, and the insertion cavity matches the telescopic plate 33. The insertion cavity facilitates the telescopic plate 33 to be inserted into the shielding plate 34.

[0030] Embodiment 2:

[0031] On the basis of the first embodiment, in this embodiment, the transmission shaft 311 drives the first pulley 71 to rotate, so that the first pulley 71 drives the active bevel gear 712 to rotate through the transmission belt 72, the second pulley 73 and the driven shaft 74, and the active bevel gear 712 drives the suction fan blades 78 to rotate through the driven bevel gear 711 and the connecting vertical shaft 79. At this time, the rotating suction fan blades 78 will cause negative pressure to be generated on the upper side of the processing box 2 to suck most of the dust above through the protective mesh plate 31, and the sucked dust will be concentratedly guided by the air guide shell 75 to the dust removal filter bag 77 for filtration, so as to prevent the dust generated during the grinding process from floating around and harming the health of the staff.

[0032] The dust suction assembly 7 includes a first pulley 71, a second pulley 73, a driven shaft 74, a suction fan blade 78, a connecting vertical shaft 79, a driven bevel gear 711, a driving bevel gear 712 and a protective shell 713. The first pulley 71 is arranged on the rear side of the annular side of the transmission shaft 311, and the second pulley 73 is installed below the first pulley 71. A transmission belt 72 is arranged between the first pulley 71 and the second pulley 73. The first pulley 71 will drive the second pulley 73 to rotate through the transmission belt 72, so that the second pulley 73 drives the driven shaft 74 to rotate. A driven shaft 74 is arranged at the front end of the second pulley 73. The driven shaft 74 is connected to the first follower ring 741 and the driving bevel gear 712 by welding. The driven shaft 74 will drive the driving bevel gear 712 to rotate. The driving bevel gear 712 is arranged at the front end of the driven shaft 74. The driving bevel gear 712 will drive the driven bevel gear 711 to rotate.

[0033] The lower side of the annular side of the active bevel gear 712 is meshed with a driven bevel gear 711, and the driven bevel gear 711 will drive the connecting vertical shaft 79 to rotate. The middle position of the lower end surface of the driven bevel gear 711 is connected with a connecting vertical shaft 79. The connecting vertical shaft 79 is connected to the driven bevel gear 711 and the second follower ring 791 by welding. The connecting vertical shaft 79 will drive the suction fan blade 78 to rotate. The suction fan blade 78 is installed at the lower end of the connecting vertical shaft 79. When the suction fan blade 78 rotates, the upper side of the inner part of the processing box 2 Negative pressure is generated so that the processing box 2 can suck most of the dust above through the protective mesh plate 31. A protective shell 713 is installed on the upper side of the processing box 2. The protective shell 713 will protect the active bevel gear 712 and the driven bevel gear 711 to prevent the active bevel gear 712 and the driven bevel gear 711 from easily adhering to dust. An air guide shell 75 is fixedly connected to the lower side of the processing box 2. The air guide shell 75 will concentrate the dust blown downward by the suction fan blades 78 into the dust removal filter bag 77.

[0034] A dust filter bag 77 is mounted on the lower side of the annular side of the air guide shell 75. The dust filter bag 77 has good air permeability and a high dust collection rate, so as to block the passing dust and prevent the dust from being directly discharged to the outside. A fixed throat clamp 771 is mounted on the upper side of the annular side of the dust filter bag 77. The fixed throat clamp 771 is convenient for the staff to disassemble, replace or clean the dust filter bag 77 at a later time. An exhaust cavity 76 is opened on the lower side of the rear end face of the processing box 2. The exhaust cavity 76 is convenient for the air filtered by the dust filter bag 77 to be discharged to the outside. A box door 21 is installed on the lower side of the front end face of the processing box 2. When the box door 21 is opened, it is convenient for the staff to reach their hands into the lower side of the interior of the processing box 2.

[0035] A first follower ring 741 is provided on the annular side surface of the driven shaft 74, and a first limit stop cover 22 is installed on the upper side of the rear end surface of the processing box 2. The first follower ring 741 and the first limit stop cover 22 prevent the driven shaft 74 from being displaced or shaken during rotation and use. A second follower ring 791 is provided on the annular side surface of the connecting vertical shaft 79, and a second limit stop cover is installed on the lower end surface of the blocking bottom plate 7132. The second follower ring 791 and the second limit stop cover prevent the connecting vertical shaft 79 from being displaced or shaken during use. The first follower ring 741 and the second follower ring 791 Ball bearings are installed on the annular side surfaces, which reduce the rotation resistance of the first follower ring 741 and the second follower ring 791. A sealing bottom plate 7132 is installed on the bottom of the protective shell 713. The sealing bottom plate 7132 not only seals the bottom of the protective shell 713, but also supports the second follower ring 791. Support rods 7131 are symmetrically arranged on the left and right sides and the front and back sides of the annular side surfaces of the protective shell 713. The support rods 7131 are connected to the protective shell 713 by welding, and the support rods 7131 support and fix the protective shell 713.

[0036] Working principle: After the positioning keyway 5 on the annular side of the special-shaped welded pipe roller 4 is processed by an external milling machine, the staff first places the special-shaped welded pipe roller 4 on the upper end surface of the protective mesh plate 31 (reference Figure 1 ), and then the driving motor 39 can be started through the control panel, so that the driving motor 39 drives the grinding wheel 32 to rotate through the transmission shaft 311. At this time, the staff can hold the special-shaped welded pipe roller 4 and place the positioning key groove 5 close to the lower side of the annular side of the grinding wheel 32 for grinding and deburring. In this process, the shielding plate 34 will block the debris splashed upward during the grinding process to prevent the splashing debris from hurting the staff's face. When it is necessary to increase the shielding area of ​​the shielding plate 34, the staff only needs to loosen the fixing plate 34 by hand. The nut 332 is fixed, and the telescopic plate 33 can be pinched and pulled to extend it, so as to increase the shielding area of ​​the shield plate 34. When the low-speed motor 37 is controlled to rotate forward through the control panel, the low-speed motor 37 can drive the vertical screw rod 36 to rotate forward together. At this time, the vertical screw rod 36 will drive the extension plate 35 to move upward through the internal threaded through hole 351, and the extension plate 35 will drive the shield plate 34 to move upward together. Similarly, when the low-speed motor 37 is controlled to reverse, the extension plate 35 can drive the shield plate 34 to move upward. The second belt pulley 73 is driven by the transmission shaft 711 to rotate, so that the first belt pulley 71 drives the second belt pulley 73 to rotate through the transmission belt 72, and the second belt pulley 73 drives the driving bevel gear 712 to rotate through the driven shaft 74, thereby making the driving bevel gear 712 drive the suction fan blade 78 to rotate through the driven bevel gear 711 and the connecting vertical shaft 79. At this time, the rotating suction fan blade 78 will cause negative pressure to be generated on the upper side of the processing box 2, so that the processing box 2 can suck most of the dust above through the protective mesh plate 31, and the sucked in dust will be concentratedly guided by the air guide shell 75 to the dust filter bag 77 for filtration, and the filtered air will be discharged to the outside through the exhaust chamber 76, so as to prevent the dust generated during the grinding process from scattering around and harming the health of the staff. At a later stage, the staff only needs to open the box door 21 and disassemble the fixed throat hoop 771, and the dust filter bag 77 can be disassembled, taken out, cleaned or replaced.

[0037] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A keyway processing device for a special-shaped welded pipe mold, comprising a fixed base plate (1), a processing box (2), a special-shaped welded pipe rolling roller (4) and a positioning keyway (5), characterized in that: The upper end surface of the fixed base plate (1) is fixedly connected to a processing box (2); the upper side of the rear end surface of the processing box (2) is fixedly connected to a fixed back plate (6); a special-shaped welded pipe roller (4) is placed on the upper end of the processing box (2); and a positioning key groove (5) is provided on the annular side surface of the special-shaped welded pipe roller (4); A grinding component (3) for removing burrs from the upper end of the positioning key slot (5) is arranged on the front side of the fixed back plate (6), and a dust suction component (7) for sucking most of the dust generated during the grinding process is arranged inside the processing box (2); A low-speed motor (37) is mounted on the upper end surface of the fixed back plate (6); a vertical screw rod (36) is connected to the lower end of the low-speed motor (37); an extension plate (35) is provided on the lower side of the annular side surface of the vertical screw rod (36); a shield plate (34) is connected to the front end of the extension plate (35); A telescopic plate (33) is inserted into the shielding plate (34), and the telescopic plate (33) and the shielding plate (34) are both arc-shaped. An external threaded rod (331) is provided at the rear side of the upper end surface of the telescopic plate (33), and a fixing nut (332) is installed on the annular side surface of the external threaded rod (331). A slot (341) is provided on the upper end surface of the shielding plate (34), and the slot (341) matches the external threaded rod (331). An internal threaded through hole (351) is provided at the rear side of the extension plate (35).

2. The keyway processing device for a special-shaped welded pipe mold according to claim 1, characterized in that: The grinding assembly (3) comprises a grinding wheel (32), a motor support frame (38), a driving motor (39) and a transmission shaft (311); the upper side of the rear end surface of the fixed back plate (6) is fixedly connected to the motor support frame (38); the rear end surface of the motor support frame (38) is mounted with the driving motor (39); the front end of the driving motor (39) is connected to the transmission shaft (311); the front end of the transmission shaft (311) is mounted with the grinding wheel (32); and a protective mesh plate (31) is placed on the upper end surface of the processing box (2).

3. The keyway processing device for a special-shaped welded pipe mold according to claim 2, characterized in that: The dust collection assembly (7) comprises a first pulley (71), a second pulley (73), a driven shaft (74), a suction fan blade (78), a connecting vertical shaft (79), a driven bevel gear (711), a driving bevel gear (712) and a protective shell (713); the first pulley (71) is arranged on the rear side of the annular side surface of the transmission shaft (311); the second pulley (73) is installed below the first pulley (71); the driven shaft (74) is arranged at the front end of the second pulley (73); the driving bevel gear (712) is arranged at the front end of the driven shaft (74); the driven bevel gear (711) is meshed with the lower side of the annular side surface of the driving bevel gear (712); the connecting vertical shaft (79) is connected to the middle position of the lower end surface of the driven bevel gear (711); the suction fan blade (78) is installed at the lower end of the connecting vertical shaft (79); and the protective shell (713) is installed on the upper side of the processing box (2).

4. The keyway processing device for a special-shaped welded pipe mold according to claim 1, characterized in that: An air guide shell (75) is fixedly connected to the lower side of the interior of the processing box (2); a dust filter bag (77) is mounted on the lower side of the annular side of the air guide shell (75); and a fixed throat clamp (771) is mounted on the upper side of the annular side of the dust filter bag (77); an exhaust cavity (76) is provided on the lower side of the rear end surface of the processing box (2); a box door (21) is installed on the lower side of the front end surface of the processing box (2); and a limiting groove (61) is provided on the upper side of the front end surface of the fixed back plate (6).

5. The keyway processing device for a special-shaped welded pipe mold according to claim 3, characterized in that: The driven shaft (74) is provided with a first follower ring (741) on the annular side surface, the upper side of the rear end surface of the processing box (2) is provided with a first limit stop cover (22), the annular side surface of the connecting vertical shaft (79) is provided with a second follower ring (791), the bottom of the protective shell (713) is provided with a blocking bottom plate (7132), the left and right sides and the front and rear sides of the annular side surface of the protective shell (713) are symmetrically provided with support rods (7131), and a transmission belt (72) is provided between the first pulley (71) and the second pulley (73).

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