CN219640908U

CN219640908U - Screw thread measuring mechanism

Info

Publication number: CN219640908U
Application number: CN202321264270.4U
Authority: CN
Inventors: 郑双飞
Original assignee: Wuxi Wannaite Automation Equipment Co ltd
Current assignee: Wuxi Wannaite Automation Equipment Co ltd
Priority date: 2023-05-23
Filing date: 2023-05-23
Publication date: 2023-09-05
Anticipated expiration: 2033-05-23

Abstract

The utility model relates to a thread measuring mechanism, which comprises a supporting plate, wherein a main shaft is arranged to penetrate through the supporting plate from top to bottom, and the main shaft is driven to rotate by a rotating power mechanism; a bottom plate is arranged below the supporting plate at intervals and hung on the bottom surface of the supporting plate by a flexible hanging mechanism; the main shaft passes through the bottom plate downwards and then is provided with a quick-change assembly, and the bottom end of the quick-change assembly is provided with a measuring head assembly; during detection, the reaction force from the measuring head assembly drives the spindle to drive the bottom plate to move upwards relative to the supporting plate for buffering and prepressing; the thread measuring mechanism is arranged on a power mechanism such as an external mechanical arm, so that the detection of threads can be realized, the detection is stable and reliable, the manual work is effectively replaced, and the practicability is good.

Description

Screw thread measuring mechanism

Technical Field

The utility model relates to the technical field of thread detection equipment, in particular to a thread measurement mechanism.

Background

Screw threads are very common machining processes, and the quality of a threaded hole needs to be effectively controlled to ensure the effectiveness and reliability of the installation of parts.

In the prior art, screw thread detection is most commonly realized by customizing a screw thread go-no-go gauge, screwing detection is respectively carried out on screw threads by one go and one stop, and the screw threads pass through the screw thread go-no-go gauge and are qualified; if the depth of the threaded hole needs to be detected, a gauge with a depth slider needs to be customized, and a touch step type is adopted to judge whether the depth of the threaded hole is qualified or not. The method has high dependence on operators, high labor intensity, very low detection efficiency and easy omission.

Disclosure of Invention

The utility model provides a thread measuring mechanism with reasonable structure aiming at the defects in the prior art, so that the thread measuring mechanism can realize detection of threads by combining with power mechanisms such as an external mechanical arm and the like, is stable and reliable in detection, effectively replaces manpower, and has good practicability.

The technical scheme adopted by the utility model is as follows:

a thread measuring mechanism comprises a supporting plate, wherein a main shaft is arranged to penetrate through the supporting plate up and down, and is driven to rotate by a rotating power mechanism; a bottom plate is arranged below the supporting plate at intervals and hung on the bottom surface of the supporting plate by a flexible hanging mechanism; the main shaft passes through the bottom plate downwards and then is provided with a quick-change assembly, and the bottom end of the quick-change assembly is provided with a measuring head assembly; during detection, the reaction force from the measuring head assembly drives the spindle to drive the bottom plate to move upwards relative to the supporting plate for buffering and prepressing.

As a further improvement of the above technical scheme:

the device also comprises a floating assembly for guiding the spindle to move up and down, and the structure of the floating assembly is as follows: the guide column is arranged between the top plate and the bottom plate; the guide posts are sleeved with upper springs, and the upper springs are arranged between the top ends of the shaft sleeves and the top plate; the top end of the main shaft is supported and mounted on the top plate through a ball bearing, and the lower part of the main shaft is rotatably assembled with the bottom plate through another bearing.

A main spring is sleeved on the main shaft between the bottom plate and the supporting plate.

The main shaft is a ball guide shaft, a shaft seat is axially and slidably arranged on the main shaft, and the shaft seat is arranged on the supporting plate in a penetrating manner through a rotating bearing; the shaft seat is driven to rotate by a rotating power mechanism.

The structure of the flexible hanging mechanism is as follows: comprises brackets which are arranged on the top surface of a supporting plate at intervals, and lifting cylinders are arranged on the single brackets; the output end of the lifting cylinder faces downwards and is provided with an upper hanging piece at the end part, and the upper hanging piece passes through the supporting plate downwards; the top surface of the bottom plate is provided with lower hanging parts which are in one-to-one correspondence with the upper hanging parts, and lifting springs are commonly arranged between the corresponding upper hanging parts and the lower hanging parts.

The structure of the quick-change assembly is as follows: the device comprises a support block fixedly sleeved at the bottom end of a main shaft, wherein a quick connector is fixedly inserted in the center of the bottom surface of the support block, and a plurality of balls are embedded in the side surface of the quick connector positioned at the bottom surface of the support block at intervals along the circumferential direction; the main shaft is of an axial hollow structure, the top end and the bottom end of the main shaft are respectively provided with an air pipe joint, the air pipe joint above is communicated with an external air source, the air pipe joint below is communicated with a hole for embedding balls on the quick connector, and the balls are driven to radially bulge or retract into the quick connector by the on-off of the external air source; the bottom end of the supporting block positioned at the axial outer part of the quick connector is also provided with bolts at intervals, a small spring is pressed between the top end of each bolt and the supporting block, the side surface of each bolt is provided with an elongated slot along the axial direction, and a limit screw is locked in the elongated slot from the side surface of the supporting block to the bolt.

The structure of the measuring head assembly is as follows: the quick-change assembly comprises a connecting block assembled with the quick-change assembly, wherein the top surface of the connecting block is provided with a jack, and the inner wall surface of the central hole of the connecting block extends inwards to form a convex ring; the bottom surface of the connecting block is provided with a torque protector, and the bottom surface of the torque protector is provided with a measuring head.

The bottom surface of the supporting plate is downwards provided with a backboard, the backboard extends downwards and exceeds the bottom plate, and a spacing distance exists between the side surface of the backboard and the end surface of the bottom plate; the guide pieces are welded on the side face of the backboard at intervals to form an integrated structure, and the bottom board is positioned between the two groups of guide pieces.

The support plate is provided with a distance measuring sensor through a support, and the distance measuring sensor faces downwards to face the bottom plate.

The structure of the rotary power mechanism is as follows: the device comprises a motor arranged on the bottom surface of a supporting plate, wherein the output end of the motor faces upwards and passes through the supporting plate to be provided with a driving wheel, the driving wheel is connected with a driven wheel through driving force of a driving belt, and the driven wheel drives a main shaft to rotate.

The beneficial effects of the utility model are as follows:

the utility model has compact and reasonable structure and convenient operation, the thread measuring mechanism is arranged on the power mechanism such as the external mechanical arm, the power mechanism drives the movement to enable the measuring head component to be positioned at the orifice of the external threaded hole, the main shaft drives the bottom plate to move upwards to generate prepressing, and then the main shaft rotates to drive the measuring head component to rotate so as to extend into the threaded hole in a relative rotating way, thereby realizing the detection of threads, realizing the stable and reliable integral detection, effectively replacing the manual work, and automatically and quickly replacing the measuring head component through the quick-change component, and having high efficiency and good practicability;

the utility model also has the following advantages:

the flexible hanging mechanism is used for balancing the gravity of the parts such as the bottom plate and the like below the supporting plate so as to assist in ensuring the precision requirement of detection;

the floating assembly has a supporting effect on the main shaft and also has a moving guiding effect on the upward movement pre-pressing of the main shaft, so that the reliability and stability of the use of the main shaft are effectively ensured while the pre-pressing is used during the screw thread detection.

Drawings

Fig. 1 is a configuration diagram of the present utility model.

Fig. 2 is a schematic structural diagram of the present utility model (the protective shell is omitted).

Fig. 3 is a schematic structural view of the flexible hanging mechanism of the present utility model.

Fig. 4 is a schematic view of the installation of the spindle, floating mechanism of the present utility model on a support plate.

Fig. 5 is a schematic structural diagram of the quick-change assembly of the present utility model.

Fig. 6 is an exploded view of the quick change assembly of the present utility model.

Fig. 7 is a schematic structural view of a probe assembly according to the present utility model.

Wherein: 1. a support plate; 2. a rotary power mechanism; 3. a flexible hanging mechanism; 4. a floating assembly; 5. a main shaft; 6. a quick change assembly; 7. a gauge head assembly; 8. a back plate; 9. a support; 10. a protective shell;

21. a motor; 22. a driving wheel; 23. a transmission belt; 24. driven wheel;

30. a bracket; 31. lifting the spring; 32. an upper hanging piece; 33. a lower hanging piece; 34. lifting and pulling the air cylinder;

40. a limit column; 41. a top plate; 42. a spring is arranged; 43. a shaft sleeve; 44. a guide post; 45. a bottom plate;

51. a main spring; 52. a ball bearing; 53. a shaft seat;

61. a support block; 62. a locking member; 63. an air pipe joint; 64. a small spring; 65. a limit screw; 66. a plug pin; 67. a quick connector; 68. a ball;

71. a joint block; 72. a torque protector; 73. measuring head; 711. a convex ring;

81. a guide.

Detailed Description

The following describes specific embodiments of the present utility model with reference to the drawings.

As shown in fig. 1 and 2, a screw thread measuring mechanism of the present embodiment includes a support plate 1, a main shaft 5 is installed penetrating the support plate 1 from top to bottom, and the main shaft 5 is driven to rotate by a rotation power mechanism 2; a bottom plate 45 is arranged below the supporting plate 1 at intervals, and the bottom plate 45 is hung on the bottom surface of the supporting plate 1 by a flexible hanging mechanism 3; the spindle 5 passes through the bottom plate 45 downwards and then is provided with a quick-change assembly 6, and the bottom end of the quick-change assembly 6 is provided with a measuring head assembly 7; during detection, the reaction force from the measuring head assembly 7 drives the spindle 5 to drive the bottom plate 45 to move upwards relative to the supporting plate 1 to buffer pre-pressing.

The screw thread measuring mechanism is arranged on a power mechanism such as an external mechanical arm, the power mechanism drives the measuring head assembly 7 to move so that the measuring head assembly 7 is positioned at an orifice of an external threaded hole, the spindle 5 drives the bottom plate 45 to move upwards to generate prepressing, and then the spindle 5 rotates to drive the measuring head assembly 7 to rotate so as to relatively rotate and stretch into the threaded hole, so that the detection of threads is realized.

In this embodiment, the flexible mounting mechanism 3 is used to balance the gravity of the bottom plate 45 and other components below the support plate 1, so as to assist in ensuring the accuracy requirement of detection.

As shown in fig. 4, the device further comprises a floating assembly 4 for guiding the spindle 5 to move up and down, wherein the floating assembly 4 is configured as follows: comprises a top plate 41 which is arranged above the supporting plate 1 at intervals, and a guide post 44 is commonly arranged between the top plate 41 and a bottom plate 45; shaft sleeves 43 which are in one-to-one correspondence with the guide posts 44 and are used for the guide posts 44 to pass through are arranged through the support plate 1, and upper springs 42 are sleeved on the guide posts 44 positioned between the top ends of the shaft sleeves 43 and the top plate 41; the top end of the main shaft 5 is supported and mounted on the top plate 41 through a ball bearing 52, and the lower part of the main shaft 5 is rotatably assembled with the bottom plate 45 through another bearing, so that the floating assembly 4 forms structural support for the main shaft 5, and meanwhile, the rotation smoothness of the main shaft 5 is effectively ensured.

The floating assembly 4 plays a supporting role on the main shaft 5 and also plays a moving guiding role for upward movement pre-pressing of the main shaft 5, so that the reliability and stability of the main shaft 5 are effectively ensured while the pre-pressing is used during the screw thread detection.

When the bottom end of the main shaft 5 is moved upwards relative to the support plate 1 by the reaction force, the floating assembly 4 moves upwards synchronously, the assembly between the guide post 44 and the shaft sleeve 43 forms a moving guide, and the reliability and stability of the movement in the up-down direction are effectively ensured.

In this embodiment, a limit post 40 may be further installed between the top surface of the support plate 1 and the top plate 41 to limit the distance between the relative upward movement of the spindle 5.

The main spring 51 is sleeved on the main shaft 5 between the bottom plate 45 and the supporting plate 1, when the main shaft 5 moves upwards relative to the supporting plate 1, the main spring 51 is pressed, and when the reaction force applied to the bottom end of the main shaft 5 is reduced or eliminated, the compressed main spring 51 drives the main shaft 5 to return downwards relative to the supporting plate 1.

The main shaft 5 is a ball guide shaft, the main shaft 5 is axially and slidably provided with a shaft seat 53, and the shaft seat 53 is penetratingly arranged on the support plate 1 through a rotating bearing, so that the axial movement of the main shaft 5 relative to the support plate 1 and the relative rotation in a horizontal plane are realized; the shaft seat 53 is driven to rotate by the rotating power mechanism 2, and the rotation of the shaft seat 53 drives the main shaft 5 to synchronously rotate.

As shown in fig. 3, the flexible hanging mechanism 3 has the structure that: comprises brackets 30 which are arranged on the top surface of the supporting plate 1 at intervals, and lifting cylinders 34 are arranged on the single brackets 30; the output end of the lifting cylinder 34 is downward and is provided with an upper hanging piece 32 at the end part, and the upper hanging piece 32 passes through the supporting plate 1 downwards; the lower hanging members 33 corresponding to the upper hanging members 32 one by one are mounted on the top surface of the bottom plate 45, and the lifting springs 31 are mounted between the corresponding upper hanging members 32 and lower hanging members 33.

In the present embodiment, the bottom plate 45 is supported by the lift cylinder 34 via the lift spring 31, and the lift spring 31 is provided to buffer the relative movement of the bottom plate 45 with respect to the support plate 1.

In this embodiment, the upper hanging member 32 and the lower hanging member 33 may be provided with hanging holes, respectively, and the end of the lifting spring 31 may be mounted by being engaged with the hanging holes.

As shown in fig. 5 and 6, the quick-change assembly 6 has the following structure: the device comprises a support block 61 fixedly sleeved at the bottom end of a main shaft 5, a quick connector 67 is fixedly inserted in the center of the bottom surface of the support block 61, and a plurality of balls 68 are embedded in the side surface of the quick connector 67 positioned at the bottom surface of the support block 61 at intervals along the circumferential direction; the main shaft 5 is of an axial hollow structure, the top end and the bottom end of the main shaft 5 are respectively provided with an air pipe joint 63, the upper air pipe joint 63 is communicated with an external air source, the lower air pipe joint 63 is communicated with a hole for embedding the ball 68 on the quick joint 67, and the ball 68 is driven to radially bulge or retract into the quick joint 67 by the on-off of the external air source; the bottom end of the supporting block 61 positioned at the axial outer part of the quick connector 67 is also inserted with a bolt 66 at intervals, a small spring 64 is pressed between the top end of the bolt 66 and the supporting block 61, a long groove along the axial direction is arranged on the side surface of the bolt 66, and a limit screw 65 is locked in the long groove facing the bolt 66 from the side surface of the supporting block 61.

In this embodiment, the driving balls 68 may be arranged to radially protrude with respect to the quick connector 67 when the external air source is in operation, and form a snap-fit engagement with the external fitting via the balls 68, whereas when the external air source is removed, the balls 68 will retract away from the external fitting under the action of an external force, thereby achieving a quick-fit between the quick-change assembly 6 and the external fitting.

Of course, the action of the external air source can be reversed, for example, the balls 68 are kept radially outwards protruded relative to the quick connector 67 under the action of the elastic member, and then are engaged with the external fitting through the balls 68; when the external air source works, the air pressure drives the balls 68 to retract relative to the quick connector 67, the elastic piece is compressed, and at the moment, the balls 68 are separated from the external fitting piece; a quick-fit between the quick-change assembly 6 and the external fitting is also achieved.

When the quick-change assembly 6 is assembled with an external assembly, in this embodiment, the quick-change assembly 6 is assembled with the engagement block 71 in the measuring head assembly 7, the end of the quick-change joint 67 extends into the central hole of the engagement block 71 during assembly, positioning is achieved by assembling the plug 66 with the insertion hole on the engagement block 71, and meanwhile, the quick-change assembly is achieved by forming a clamping assembly with the convex ring 711 through the convex of the ball 68.

The supporting block 61 in this embodiment has a cylindrical structure, and the upper portion thereof is divided into two opposite halves along the longitudinal section, and the two halves are fastened via the fastening member 62 after being disposed around the spindle 5, so as to realize the locking and fixing between the supporting block 61 and the spindle 5.

As shown in fig. 7, the gauge head assembly 7 has the structure that: the quick-change assembly comprises a connecting block 71 assembled with the quick-change assembly 6, wherein the top surface of the connecting block 71 is provided with a jack, and the inner wall of the central hole of the connecting block 71 extends inwards to form a convex ring 711; the bottom surface of the connecting block 71 is provided with a torque protector 72, and the bottom surface of the torque protector 72 is provided with a measuring head 73.

The bottom surface of the supporting plate 1 is downwards provided with a backboard 8, the backboard 8 extends downwards and exceeds the bottom plate 45, and a spacing distance exists between the side surface of the backboard 8 and the end surface of the bottom plate 45; the side surfaces of the back plate 8 are welded with guide pieces 81 at intervals to form an integrated structure, the bottom plate 45 is positioned between the two groups of guide pieces 81, and the guide pieces 81 provide limit guide for the up-and-down movement of the bottom plate 45.

The support plate 1 is provided with distance measuring sensors via a support, the distance measuring sensors face downwards against the bottom plates 45, and the distance between the bottom plates 45 is detected by the distance measuring sensors for feeding back the thread depth in the thread detection.

The structure of the rotary power mechanism 2 is as follows: the motor 21 is arranged on the bottom surface of the supporting plate 1, the output end of the motor 21 faces upwards and passes through the supporting plate 1 to be assembled with a driving wheel 22, the driving wheel 22 is connected with a driven wheel 24 through a driving belt 23 in a power way, and the driven wheel 24 drives the main shaft 5 to rotate.

In this embodiment, the driven wheel 24 is fixedly installed on the shaft seat 53, and the driven wheel 24 drives the shaft seat 53 to rotate, so as to drive the spindle 5 inside the shaft seat 53 to rotate.

In the utility model, a main shaft 5, a rotary power mechanism 2, a flexible hanging mechanism 3, a floating assembly 4 and the like are contained in a protective shell 10 to form an integral module structure, and the end part of a supporting plate 1 extends out of the protective shell 10 for being connected with power mechanisms such as an external mechanical arm and the like.

The application mode of the utility model is as follows:

the screw thread measuring mechanism is arranged on an external mechanical arm, the external mechanical arm drives the screw thread measuring mechanism to move until the measuring head assembly 7 is positioned at the orifice of the screw hole to be measured, and a certain contact force is applied to the orifice of the screw hole, so that the main shaft 5 passively drives the bottom plate 45 to move upwards to generate pre-compression with the screw hole, and the main spring 51 is compressed; along with the work of the rotary power mechanism 2, the spindle 5 and the measuring head assembly 7 are driven to rotate by the shaft seat 53, and the pre-pressing is gradually released, so that the measuring head assembly 7 is screwed into a threaded hole to be measured, and the thread detection is realized;

of course, in the actual use process, whether the threaded hole is qualified or not needs to be judged through the passable gauge head assembly 7 and the non-passable gauge head assembly 7, namely, the go gauge and the no-go gauge; in this embodiment, the quick-change assembly 6 can be used to quickly change the probe assembly 7 of different types.

The screw thread detection device is simple in operation, realizes screw thread detection, is stable and reliable in overall detection, effectively replaces manpower, can automatically and quickly replace a measuring head assembly through a quick-change assembly, and is high in efficiency and good in practicability.

The above description is intended to illustrate the utility model and not to limit it, the scope of which is defined by the claims, and any modifications can be made within the scope of the utility model.

Claims

1. Screw thread measuring mechanism, comprising a support plate (1), characterized in that: a main shaft (5) is arranged through the supporting plate (1) from top to bottom, and the main shaft (5) is driven to rotate by a rotating power mechanism (2); a bottom plate (45) is arranged below the supporting plate (1) at intervals, and the bottom plate (45) is hung on the bottom surface of the supporting plate (1) through a flexible hanging mechanism (3); the main shaft (5) passes through the bottom plate (45) downwards and is provided with a quick-change assembly (6), and the bottom end of the quick-change assembly (6) is provided with a measuring head assembly (7); during detection, the reaction force from the measuring head assembly (7) drives the spindle (5) to drive the bottom plate (45) to move upwards relative to the supporting plate (1) to buffer and pre-press.

2. A thread measurement mechanism as recited in claim 1, wherein: the device also comprises a floating assembly (4) for guiding the spindle (5) to move up and down, wherein the floating assembly (4) is structured as follows: comprises a top plate (41) which is arranged above a supporting plate (1) at intervals, wherein a guide post (44) is commonly arranged between the top plate (41) and a bottom plate (45); shaft sleeves (43) which are in one-to-one correspondence with the guide posts (44) and are penetrated by the guide posts (44) are arranged through the support plate (1), and upper springs (42) are sleeved on the guide posts (44) positioned between the top ends of the shaft sleeves (43) and the top plate (41); the top end of the main shaft (5) is supported and mounted on the top plate (41) through a ball bearing (52), and the lower part of the main shaft (5) is rotatably assembled with the bottom plate (45) through another bearing.

3. A thread measurement mechanism as recited in claim 1, wherein: a main spring (51) is sleeved on the main shaft (5) between the bottom plate (45) and the supporting plate (1).

4. A thread measurement mechanism as recited in claim 1, wherein: the main shaft (5) is a ball guide shaft, a shaft seat (53) is axially and slidably assembled on the main shaft (5), and the shaft seat (53) is installed on the supporting plate (1) in a penetrating manner through a rotating bearing; the shaft seat (53) is driven to rotate by the rotating power mechanism (2).

5. A thread measurement mechanism as recited in claim 1, wherein: the structure of the flexible hanging mechanism (3) is as follows: comprises brackets (30) which are arranged on the top surface of a supporting plate (1) at intervals, wherein lifting cylinders (34) are arranged on the single brackets (30); the output end of the lifting cylinder (34) faces downwards, an upper hanging piece (32) is arranged at the end part of the lifting cylinder, and the upper hanging piece (32) downwards penetrates through the supporting plate (1); the top surface of the bottom plate (45) is provided with lower hanging pieces (33) which are in one-to-one correspondence with the upper hanging pieces (32), and lifting springs (31) are arranged between the corresponding upper hanging pieces (32) and the lower hanging pieces (33) together.

6. A thread measurement mechanism as recited in claim 1, wherein: the quick-change assembly (6) has the structure that: the device comprises a supporting block (61) fixedly sleeved at the bottom end of a main shaft (5), a quick connector (67) is fixedly inserted in the center of the bottom surface of the supporting block (61), and a plurality of balls (68) are embedded in the side surface of the quick connector (67) positioned at the bottom surface of the supporting block (61) along the circumferential direction at intervals; the main shaft (5) is of an axial hollow structure, the top end and the bottom end of the main shaft (5) are respectively provided with an air pipe joint (63), the upper air pipe joint (63) is communicated with an external air source, the lower air pipe joint (63) is communicated with a hole for embedding a ball (68) on the quick connector (67), and the ball (68) is driven to radially bulge or retract into the quick connector (67) by the on-off of the external air source; the bottom end of the supporting block (61) positioned at the axial outer part of the quick connector (67) is also provided with a plug pin (66) at intervals, a small spring (64) is pressed between the top end of the plug pin (66) and the supporting block (61), the side surface of the plug pin (66) is provided with an elongated slot along the axial direction, and a limit screw (65) is locked in the elongated slot facing the plug pin (66) from the side surface of the supporting block (61).

7. A thread measurement mechanism as recited in claim 1, wherein: the structure of the measuring head assembly (7) is as follows: comprises a connecting block (71) assembled with a quick-change assembly (6), the top surface of the connecting block (71) is provided with a jack, and the inner wall of the central hole of the connecting block (71) extends inwards to form a convex ring (711); the bottom surface of the connecting block (71) is provided with a torque protector (72), and the bottom surface of the torque protector (72) is provided with a measuring head (73).

8. A thread measurement mechanism as recited in claim 1, wherein: the bottom surface of the supporting plate (1) is downwards provided with a back plate (8), the back plate (8) extends downwards and exceeds the bottom plate (45), and a spacing distance exists between the side surface of the back plate (8) and the end surface of the bottom plate (45); guide pieces (81) are welded on the side face of the back plate (8) at intervals to form an integrated structure, and the bottom plate (45) is positioned between the two groups of guide pieces (81).

9. A thread measurement mechanism as recited in claim 1, wherein: the support plate (1) is provided with a distance measuring sensor through a support (9), and the distance measuring sensor faces downwards to face the bottom plate (45).

10. A thread measurement mechanism as recited in claim 1, wherein: the structure of the rotary power mechanism (2) is as follows: the device comprises a motor (21) arranged on the bottom surface of a supporting plate (1), wherein the output end of the motor (21) faces upwards and passes through the supporting plate (1) to be assembled with a driving wheel (22), the driving wheel (22) is in power connection with a driven wheel (24) through a transmission belt (23), and the driven wheel (24) drives a main shaft (5) to rotate.